Javascript代码压缩细节-守望者-AIR技术交流

破晓发表于 2016-8-11 10:15:24

Javascript代码压缩细节

来源：http://div.io/topic/447<div> </div><div><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">前言</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">对于Javascript来说，提高网络下载的性能最直接的方法就是把JS文件体积减小，前边混淆压缩变量名字是方法之一，但是还有诸多可以把代码体积压小的规则，我在本篇文章会对UglifyJS所有压缩代码体积的细节整理成一条条的规则，为了方便理解，还会给出一些压缩前代码以及压缩后代码的对比（没法像自己博客那样定义格式，所以下边压缩前后的代码比较表现不明显，第一个框为压缩前代码，第二个框为压缩后代码）。由于UglifyJS里边对IF的压缩规则最多，也是最为丰富精彩的部分，放在最后边解释。 还是那样，有兴趣了解UglifyJS实现细节，看文章最后的我对它源码做的注释。 留意：<ol style="padding-left: 30px; margin-bottom: 14px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><li>下边代码样例中左侧为压缩前源码，右侧为压缩后代码，为了对比方便，下边多数的代码压缩后的变量名字没有混淆处理，同时一个压缩规则的例子尽量不混其他压缩策略进去。</li><li>我下文多处写到的表达式语句是指UglifyJS语法分析得到的simple_statement，你可以认为只要能放到逗号表达式里边的都算是simple_statement。</li></ol><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">表达式的压缩</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则1.1 表达式预计算 将可预先计算的表达式替换成其计算结果，同时要比较原来表达式以及生成后的结果的大小，取短的。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">var expr1 = 1 + 1;
var expr2 = 1 / 3;
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">var expr1 = 2;
var expr2 = 1 / 3;//由于计算出来的值0.3333333333333比1/3要长，所以不预计算
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则1.2 优化true跟false 正常情况下会把： true变成!0，节省2个字符 false变成!1，节省3个字符 有人会疑问：这里为什么不直接把true变成1，false变成0呢？因为这样会把一个布尔类型变成数字类型参与某些运算导致运行时混乱。 但是有没有什么情况比较特殊，可以把true变成1，false变成0呢？答案是有的：就是再参与==以及!=运算时。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">var expr1 = true;
var expr2 = false;
true == A;
false == A;
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">var expr1 = !0;
var expr2 = !1;
1 == A;
0 == A;
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则1.3 根据&& ||短路的特性压缩表达式<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">true && A();
false && A();
true || A();
false || A();
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">A();//返回&&第二个操作数的值
!1;//返回&&第一个操作数的值
!0;//返回||第一个操作数的值
A();//返回&&第二个操作数的值
</pre></div></div><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">运算符缩短</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则2.1 对于二元操作符===以及!==，其两个操作数都是string类型或者都是布尔类型的，可以缩短成==以及!= 留意：这里typeof A得到的结果是string类型，b instanceof B得到的结果是布尔类型~ 当然还有其他规则，这个详细看源码里边的booleanexpr函数以及isstring函数的实现，以后再写文章说一下这里。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">"object" === typeof A;
(a,b,true) !== b instanceof B;
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">"object" == typeof A;
(a,b,true) != b instanceof B;
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则2.2 缩短赋值表达式，对于a = a + b这样的赋值表达式，可以缩短成 a += b 这里说起来可能有点绕，但是想一下也很容易理解这条规则的详细判断：<ol style="padding-left: 30px; margin-bottom: 14px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><li>必须是=号赋值语句</li><li>=号左侧只能是变量，不能为表达式等</li><li>=号右侧必须为二元操作表达式，并且符号是为数组['+', '-', '/', '*', '%', '>>', '<<', '>>>', '|', '^', '&']中的元素</li><li>=号右侧的二元表达式的第一个操作数必须跟=号左侧的变量一致</li></ol><div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">a = a + b;
c = c >>> d;
a = b + c;
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">a += b;
c >>>= d;
a = b + c;
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则2.3 操作符非!的压缩 对a>=b取非可以得到a 如果转换后的结果能得到更短的代码，那就将这个取非的表达式换成转换后的表达式。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">!(a>=b)
!!!a
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">a</pre></div></div><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">去除没用的声明/引用</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则3.1 去除重复的指示性字符串 对于嵌套的作用域使用了同样的指示性字符串，其实子作用域的是可以去除的。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
"use strict";
function B(){
"use strict";
}
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
"use strict";
function B(){
}
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则3.2 去除没有使用的函数参数 参数c在函数A里边没有使用，所以直接去除c参数的声明。也许你会好奇为什么参数a也没有使用却不去掉，如果去掉参数a，就会改变了b所在的参数位置，例如：调用A(1,2)时候，本来b应该是2的，如果去除参数a，这个时候b就会变成1，这样会引起错误。因此UglifyJS在去除函数参数的时候都是从后往前扫描变量在函数里边的引用。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(a, b, c){
b++;
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(a, b){
b++;
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则3.3 去除函数表达式冗余的函数名 对于一个函数表达式，如果其函数体没有引用自身名字递归调用，那么这个函数名可以去除，使之变为匿名函数。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">(function A(){
A();
})();
(function B(){
c++;
})();
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">(function A(){
A();
})();
(function(){
c++;
})();
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则3.4 去除没用的块 如果块里边没有语句或者只有一条语句，那么这个块可以去掉{}。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">while (f){
{
A();
}
}
while (f){
{
}
}
if (A){
B();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">while (f)
A();
while (f)
;
if (A)
B();
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则3.5 去除没有使用的break; switch最后一个case/default分支块的最后一个语句如果是break;的话，可以忽略，如果break后边带有标签则不能去除。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">switch(A){
case 1:
break;
case 2:
break;
}

label:
switch(A){
case 1:
break;
case 2:
break label;
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">switch(A){
case 1:
break;
case 2://这里最后的break;可以忽略
}

label:
switch(A){
case 1:
break;
case 2:
break label;//带标签的break不可以忽略
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则3.6 去除没有引用的label<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">label1:var a = 1;
label2:while (true){
break label2;
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">var a = 1;
label2:while (true){
break label2;//label2被引用不可以去掉
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则3.7 去除没作用的toString函数调用 这个规则在某些条件可能会有不安全的问题产生，因此UglifyJS只有在你明确调用时带上--unsafe的参数才会做这个压缩<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">(typeof A).toString();
("A" + "B").toString();
var expr = "str".toString();
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">(typeof A);
"AB";
var expr = "str";
</pre></div></div><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">while压缩</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则很简单： 规则4.1 去除根本不会执行的while循环：while(false){} 规则4.2 while(true)变成for(;;)，可以缩短4个字符，:)<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">while(false){
A();
B();
}
while(true){
C();
D();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">//while(false)被压缩忽略掉

for(;;){
C();
D();
}
</pre></div><div> </div></div></div>

破晓发表于 2016-8-11 10:16:07

<h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">条件表达式</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">条件表达式使用了三元运算符?:，例如：cond ? yes() : no()<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则5.1 如果cond前边有非运算，那么考虑把非去掉，然后调转yes()跟no()的位置<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">!cond ? yes() : no();
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">cond ? no() : yes();
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则5.2 如果cond是一个常数值，那么可以直接缩短为yes()或者no();<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">true ? yes() : no();
false ? yes() : no();
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">yes();
no();
</pre></div></div><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">语句块压缩</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">函数体，with都会生成一个语句块，下边规则是针对语句块的压缩优化。<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则6.1 连续的表达式语句可以合并成一个逗号表达式 留意这里要表达式语句才可以。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
B();
C();
d = 1;
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
B(), C(), d = 1;
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则6.2 多个var声明可以压缩成一个var声明<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
var a;
var b;
var c;
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
var a, b, c;
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则6.3 return之后的非变量声明以及非函数声明的语句可以去除 在块里边return之后的语句是不会被执行到的可以被去除，但是Javascript中在块里边无论什么地方声明都可以，因此return之后的声明是不能去掉的。 当然这里不仅仅是return之后的语句可以去除，还有throw，break，continue之后的语句也适用于这条规则。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
return false;
var a = 1;
function B(){}
expr += 1;
a = 3;
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
function B(){}
return false;
var a = 1;
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则6.4 合并块末尾的return语句及其前边的多条表达式语句。 其实这条规则看起来并不会使最后生成的代码缩小。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
B();
C();
return D();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">function A(){
return B(), C(), D();
}
</pre></div></div><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif;">IF分支优化</h2><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">接下来开始复杂丰富多彩的IF分支压缩！<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则7.1 去除没用的if/else分支 如果if的条件是可预计算得到的常数结果，那么就可以忽略掉没用的if/else分支<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (true){
A();
}else{
B();
}
if (false){
C();
}else{
D();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">A();
D();
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则7.2 去除空的if/else分支 如果是if分支是空的话，把条件取非，else分支反转成if分支即可<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (A){
B();
}else{
}
if (C){
}else{
D();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (A){
B();
}
if (!C){
D();
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则7.3 尝试反转if/else分支，看看生成代码是否更短 尝试对if条件取非，如果能得到更短的代码，那就反转if/else分支<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (!c){
A();
}else{
B();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (c){
B();
}else{
A();
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则7.4 如果if块里边只有一个if语句，并且else块为空，那么可以合并这两个if<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (A){
if (B){
C();
}
}else{
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (A && B){
C();
}
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则7.5 如果if最后一个语句是跳出控制语句，那么可以把else块的内容提到else外边，然后去掉else<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (A){
B();
return;
}else{
C();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (A){
B();
return;
}
C();
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则7.6 如果if/else里边都只有一句return语句，则可以合并这两句return<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (A){
return B();
}else{
return C();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">return A ? B() : C();
</pre></div></div><p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则7.7 如果if跟else里边都只有一句表达式语句，则可以化成条件表达式，然后走规则5.1跟5.2进一步压缩<p style="margin-top: 18px; margin-bottom: 18px; color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;">规则7.8 如果if/else其中一个块为空，另一个块只有一条语句，则可以化成||或者&&的表达式。<div style="color: rgb(51, 51, 51); font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 16px; line-height: 27.2px;"><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">if (A){
B();
}else{
}
if (C){
}else{
D();
}
</pre></div><div><pre style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; padding: 6px 10px; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);">A && B();
C || D();
</pre></div><div> </div></div>

破晓发表于 2016-8-11 10:17:13

<div class="topic-firstfloor-detail type" style="font-family: "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; counter-reset: chapter 0 section 0 subsection 0; font-size: 16px; color: rgb(51, 51, 51); padding-top: 20px; padding-bottom: 20px; margin-top: 10px; line-height: 1.7; width: auto; margin-left: auto !important; margin-right: auto !important;"><h2 style="font-size: 26px; margin-top: 20px; margin-bottom: 20px; counter-reset: section 0; font-weight: normal;">代码注释</h2>有兴趣的自己展开看源码~<pre class="prettyprint lang-javascript prettyprinted" style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; padding: 6px 10px; border: 1px solid rgb(221, 221, 221); font-size: 12px; line-height: 18px; overflow: auto; border-radius: 3px; word-break: break-all; background-color: rgb(248, 248, 248);"><code style="font-family: consolas, monaco, menlo, "courier new", courier, monospace; display: inline-block; line-height: 1.5; border: 0px none; border-radius: 0px; font-size: inherit; background: none;">//优化AST树，使生成的代码尽可能短
//@raphealguo
//官网记录了优化的内容，但是不一定在squeeze_1里边做的，这里只是列出来方便比对，
//这里分别用序号标明各个规则，在下边源码注释中会使用规则X的字眼来引用。
/*
1. foo[“bar”] ==> foo.bar
2. remove block brackets {}
3. join consecutive var declarations: var a = 10; var b = 20; ==> var a=10,b=20;
4. resolve simple constant expressions: 1 +2 * 3 ==> 7. We only do the replacement if the result occupies less bytes; for example 1/3 would translate to 0.333333333333, so in this case we don’t replace it.
5. consecutive statements in blocks are merged into a sequence; in many cases, this leaves blocks with a single statement, so then we can remove the block brackets.
6. various optimizations for IF statements:
7. if (foo) bar(); else baz(); ==> foo?bar():baz();
8. if (!foo) bar(); else baz(); ==> foo?baz():bar();
9. if (foo) bar(); ==> foo&&bar();
10. if (!foo) bar(); ==> foo||bar();
11. if (foo) return bar(); else return baz(); ==> return foo?bar():baz();
12. if (foo) return bar(); else something(); ==> {if(foo)return bar();something()}
13. remove some unreachable code and warn about it (code that follows a return, throw, break or continue statement, except function/variable declarations).
14. act a limited version of a pre-processor (c.f. the pre-processor of C/C++) to allow you to safely replace selected global symbols with specified values. When combined with the optimisations above this can make UglifyJS operate slightly more like a compilation process, in that when certain symbols are replaced by constant values, entire code blocks may be optimised away as unreachable.
*/

var warn = function(){};

//比较ast1跟ast2两棵树最后生成的代码谁比较短，谁短用谁
function best_of(ast1, ast2) {
return gen_code(ast1).length > gen_code(ast2[0] == "stat" ? ast2[1] : ast2).length ? ast2 : ast1;
};

//当前块里边的最后一条语句
function last_stat(b) {
if (b[0] == "block" && b[1] && b[1].length > 0)
 return b[1][b[1].length - 1];
return b;
}

function aborts(t) {
if (t) switch (last_stat(t)[0]) {
 case "return":
 case "break":
 case "continue":
 case "throw":
 return true;
}
};

//看看表达式运算结果是否为布尔类型
function boolean_expr(expr) {
return ( (expr[0] == "unary-prefix"
 && member(expr[1], [ "!", "delete" ])) ||

 (expr[0] == "binary"
 && member(expr[1], [ "in", "instanceof", "==", "!=", "===", "!==", "<", "<=", ">=", ">" ])) ||

 (expr[0] == "binary"
 && member(expr[1], [ "&&", "||" ])
 && boolean_expr(expr[2])
 && boolean_expr(expr[3])) ||

 //三元运算符
 (expr[0] == "conditional"
 && boolean_expr(expr[2])
 && boolean_expr(expr[3])) ||

 //赋值语句
 (expr[0] == "assign"
 && expr[1] === true
 && boolean_expr(expr[3])) ||

 //逗号表达式
 (expr[0] == "seq"
 && boolean_expr(expr[expr.length - 1]))
 );
};

//看看树枝是不是空树枝
function empty(b) {
return !b || (b[0] == "block" && (!b[1] || b[1].length == 0));
};

//看看当前AST节点是不是string类型
function is_string(node) {
return (node[0] == "string" ||

//typeof得到结果也是字符串
 node[0] == "unary-prefix" && node[1] == "typeof" ||

 //字符串a+字符串b得到字符串
 node[0] == "binary" && node[1] == "+" &&
 (is_string(node[2]) || is_string(node[3])));
};

//尝试将表达式节点化简
var when_constant = (function(){

var $NOT_CONSTANT = {};

// this can only evaluate constant expressions.If it finds anything
// not constant, it throws $NOT_CONSTANT.
//尽可能的把表达式化成计算结果
//a = 3*4 => a = 12;
//但是不一定这样优化会有效，例如：
//a = 1/3 => a = 0.33333可能会变得更长
function evaluate(expr) {
 switch (expr[0]) {
 case "string":
 case "num":
 return expr[1];//单个数字跟字符串不用化简了
 case "name":
 case "atom":
 switch (expr[1]) {//这里要对字符串转真正的Javascript值才能参与计算
 case "true": return true;
 case "false": return false;
 case "null": return null;
 }
 break;
 case "unary-prefix"://一元操作符
 switch (expr[1]) {
 case "!": return !evaluate(expr[2]);
 case "typeof": return typeof evaluate(expr[2]);
 case "~": return ~evaluate(expr[2]);
 case "-": return -evaluate(expr[2]);
 case "+": return +evaluate(expr[2]);
 }
 break;
 case "binary"://二元操作符
 var left = expr[2], right = expr[3];
 switch (expr[1]) {
 case "&&" : return evaluate(left) && evaluate(right);
 case "||" : return evaluate(left) || evaluate(right);
 case "|" : return evaluate(left) | evaluate(right);
 case "&" : return evaluate(left) & evaluate(right);
 case "^" : return evaluate(left) ^ evaluate(right);
 case "+" : return evaluate(left) + evaluate(right);
 case "*" : return evaluate(left) * evaluate(right);
 case "/" : return evaluate(left) / evaluate(right);
 case "%" : return evaluate(left) % evaluate(right);
 case "-" : return evaluate(left) - evaluate(right);
 case "<<" : return evaluate(left) << evaluate(right);
 case ">>" : return evaluate(left) >> evaluate(right);
 case ">>>" : return evaluate(left) >>> evaluate(right);
 case "==" : return evaluate(left) == evaluate(right);
 case "===" : return evaluate(left) === evaluate(right);
 case "!=" : return evaluate(left) != evaluate(right);
 case "!==" : return evaluate(left) !== evaluate(right);
 case "<" : return evaluate(left) < evaluate(right);
 case "<=" : return evaluate(left) <= evaluate(right);
 case ">" : return evaluate(left) > evaluate(right);
 case ">=" : return evaluate(left) >= evaluate(right);
 case "in" : return evaluate(left) in evaluate(right);
 case "instanceof" : return evaluate(left) instanceof evaluate(right);
 }
 }
 //其他情况都抛出错误，告诉外界没法化简
 throw $NOT_CONSTANT;
};

return function(expr, yes, no) {
 try {
 //参数将表达式expr化成val
 var val = evaluate(expr), ast;

 //如果能够成功就到这里
 switch (typeof val) {
 //运算的结果只能是null|string|number|boolean
 case "string": ast =[ "string", val ]; break;
 case "number": ast =[ "num", val ]; break;
 case "boolean": ast =[ "name", String(val) ]; break;//这里是因为计算后的结果可能是 true false 但是对于AST叶子来说应该是一个name的节点才对
 default:
 if (val === null) { ast = [ "atom", "null" ]; break; }
 //没有认出的类型抛出错误
 throw new Error("Can't handle constant of type: " + (typeof val));
 }
 return yes.call(expr, ast, val);
 } catch(ex) {
 if (ex === $NOT_CONSTANT) {//如果是真的化简失败
 if (expr[0] == "binary"
 && (expr[1] == "===" || expr[1] == "!==")
 && ((is_string(expr[2]) && is_string(expr[3]))
 || (boolean_expr(expr[2]) && boolean_expr(expr[3])))) {
 //"a" === "b""a" !== "b" 
 //true === true false !== true
 //这两种都可以把 
 // === 变成 == 
 // !== 变成 !=
 expr[1] = expr[1].substr(0, 2);
 }
 else if (no && expr[0] == "binary"
 && (expr[1] == "||" || expr[1] == "&&")) {
 // the whole expression is not constant but the lval may be...
 // || &&的短路操作
 try {
 //看看 expr && expr 跟 expr && expr

 var lval = evaluate(expr[2]);//如果expr能够化简！
 //如果 expr == "&&"
 //那么expr就是expr 否则还是说expr
 expr = ((expr[1] == "&&" && (lval ? expr[3] : lval)) ||

 //如果 expr == "||"
 //如果 expr == true
 //那么expr就是expr 否则是expr
 (expr[1] == "||" && (lval ? lval : expr[3])) ||
 expr);
 } catch(ex2) {
 //不能化简第一个操作数那就没办法了~
 // IGNORE... lval is not constant
 }
 }
 return no ? no.call(expr, expr) : null;
 }
 else throw ex;
 }
};

})();

function warn_unreachable(ast) {
if (!empty(ast))
 warn("Dropping unreachable code: " + gen_code(ast, true));
};

//预处理if树枝
/*
把
if (x) {
 blah();
 return y;
}
foobar();

变成：

if (x) {
 blah();
 return y;
} else {
 foobar();
}

为什么？因为对于IF/ELSE的结构，在squeeze_1会有很多特殊的处理，这里把它强制转成带else分支可能在后续的压缩过程可以得到更好的优化
*/
function prepare_ifs(ast) {
var w = ast_walker(), walk = w.walk;
//下边已经解释prepare_ifs要做的事情了

// In this first pass, we rewrite ifs which abort with no else with an
// if-else.For example:
//
// if (x) {
// blah();
// return y;
// }
// foobar();
//
// is rewritten into:
//
// if (x) {
// blah();
// return y;
// } else {
// foobar();
// }
function redo_if(statements) {
 statements = MAP(statements, walk);

 //扫描当前语句块里边的if树枝
 //if的AST树枝是：["if", cond, body, belse]
 for (var i = 0; i < statements.length; ++i) {
 var fi = statements[i];
 if (fi[0] != "if") continue;

 if (fi[3]) continue;//如果有else分支，那不用动

 var t = fi[2];
 /*
function aborts(t) {
if (t) switch (last_stat(t)) {
 case "return":
 case "break":
 case "continue":
 case "throw":
 return true;
}
};
*/
//看看语句块的最后一句是不是跳转出if
 if (!aborts(t)) continue;

 //为什么这里要walk呢？
 //因为有可能 if((function(){if(xxx){xxx}})()) 在cond里边也可能有if语句
 var conditional = walk(fi[1]);

 //把后边的语句变成一个else的树枝
 var e_body = redo_if(statements.slice(i + 1));

 //如果超过一行语句需要生成一个block
 var e = e_body.length == 1 ? e_body[0] : [ "block", e_body ];

 //返回优化后的AST树
 return statements.slice(0, i).concat([ [
 fi[0], // "if"
 conditional, // conditional
 t, // then 为什么t不用walk? @unkowned
 e // else
 ] ]);
 }

 return statements;
};

function redo_if_lambda(name, args, body) {
 body = redo_if(body);
 return [ this[0], name, args, body ];
};

function redo_if_block(statements) {
 return [ this[0], statements != null ? redo_if(statements) : null ];
};

return w.with_walkers({
 "defun": redo_if_lambda,
 "function": redo_if_lambda,
 "block": redo_if_block,
 "splice": redo_if_block,
 "toplevel": function(statements) {
 return [ this[0], redo_if(statements) ];
 },
 "try": function(t, c, f) {
 return [
 this[0],
 redo_if(t),
 c != null ? [ c[0], redo_if(c[1]) ] : null,
 f != null ? redo_if(f) : null
 ];
 }
}, function() {
 return walk(ast);
});
}

//优化AST树！使得生成的代码最小化
function squeeze_1(ast, options) {
//覆盖默认参数
options = defaults(options, {
 make_seqs : true,
 dead_code : true,
 no_warnings : false,
 keep_comps: true,
 unsafe : false
});

//拿到遍历器
var w = ast_walker(), walk = w.walk, scope;

//对表达式取非
function negate(c) {
//得到一个非的表达式
 var not_c = [ "unary-prefix", "!", c ];
 switch (c[0]) {
 case "unary-prefix":
 //!c的非就是c
 return c[1] == "!" && boolean_expr(c[2]) ? c[2] : not_c;
 case "seq":
 //a,b,!c的非就是：a,b,c
 c = slice(c);
 c[c.length - 1] = negate(c[c.length - 1]);
 return c;
 case "conditional":
 //a ? b : c的非就是 a ? !b : !c;
 return best_of(not_c, [ "conditional", c[1], negate(c[2]), negate(c[3]) ]);
 case "binary":
 //二元操作符的非
 var op = c[1], left = c[2], right = c[3];
 if (!options.keep_comps) switch (op) {
 case "<=": return [ "binary", ">", left, right ];
 case "<" : return [ "binary", ">=", left, right ];
 case ">=": return [ "binary", "<", left, right ];
 case ">" : return [ "binary", "<=", left, right ];
 }
 switch (op) {
 case "==": return [ "binary", "!=", left, right ];
 case "!=": return [ "binary", "==", left, right ];
 case "===" : return [ "binary", "!==", left, right ];
 case "!==" : return [ "binary", "===", left, right ];
 //a && b 非就是 !a || !b
 //a || b 的非就是 a && b
 case "&&": return best_of(not_c, [ "binary", "||", negate(left), negate(right) ]);
 case "||": return best_of(not_c, [ "binary", "&&", negate(left), negate(right) ]);
 }
 break;
 }
 //其他情况直接前边加!
 return not_c;
};

//条件最短化
//c ? t : e
//if (c) {t} else {e}
function make_conditional(c, t, e) {
 var make_real_conditional = function() {
 if (c[0] == "unary-prefix" && c[1] == "!") {
 //如果c前边有个!
//例如：if (!c) { A() } else{ B() } 化简成： c ? B() : A();
//例如：if (!c) { A() } else{ } 化简成： c || A();
 return e ? [ "conditional", c[2], e, t ] : [ "binary", "||", c[2], t ];
 } else {
//例如：if (c) { A() } else{ B() } 化简成： c ? A() : B(); 或者 !c ? B() : A()
//例如：if (c) { A() } else{ } 化简成： c && A();
 return e ? best_of(
 [ "conditional", c, t, e ],
 [ "conditional", negate(c), e, t ]
 ) : [ "binary", "&&", c, t ];
 }
 };
 // shortcut the conditional if the expression has a constant value
 return when_constant(c, function(ast, val){
 warn_unreachable(val ? e : t);
 return (val ? t : e);
 }, make_real_conditional);
};

//移除语句块
//只有语句块里边是1条/0条语句的时候才能移除
//while(true){ { a(); } }可以化简成为 while(true){ a(); }
//while(true){ { } }可以化简成为 while(true){ }
function rmblock(block) {
 if (block != null && block[0] == "block" && block[1]) {
 if (block[1].length == 1)
 block = block[1][0];
 else if (block[1].length == 0)//返回一个空块
 block = [ "block" ];
 }
 return block;
};

function _lambda(name, args, body) {
 return [ this[0], name, args, tighten(body, "lambda") ];
};

// this function does a few things:
// 1. discard useless blocks
// 2. join consecutive var declarations
// 3. remove obviously dead code
// 4. transform consecutive statements using the comma operator
// 5. if block_type == "lambda" and it detects constructs like if(foo) return ... - rewrite like if (!foo) { ... }
//压缩语句块
function tighten(statements, block_type) {
 statements = MAP(statements, walk);

 //去除空白的block
 statements = statements.reduce(function(a, stat){
 if (stat[0] == "block") {
 if (stat[1]) {
 a.push.apply(a, stat[1]);
 }
 } else {
 a.push(stat);
 }
 return a;
 }, []);

 statements = (function(a, prev){
 //var a;var b;优化成 var a, b;
 statements.forEach(function(cur){
 if (prev && ((cur[0] == "var" && prev[0] == "var") ||
 (cur[0] == "const" && prev[0] == "const"))) {
 prev[1] = prev[1].concat(cur[1]);
 } else {
 a.push(cur);
 prev = cur;
 }
 });
 return a;
 })([]);

 //--no-dead-code 默认 UglifyJS 将会删除不被用到的代码，传入该参数禁用此功能。
 //dead_code 默认是true
 /*
 function A(){
var a;
return b;
//这之后的语句考虑忽略掉，但是要看看后边有没有函数声明跟变量声明
a = 1;
function B(){}
 }
*/
 if (options.dead_code) statements = (function(a, has_quit){
 statements.forEach(function(st){
 if (has_quit) {
 if (st[0] == "function" || st[0] == "defun") {
 a.push(st);
 }
 else if (st[0] == "var" || st[0] == "const") {
 if (!options.no_warnings)
 warn("Variables declared in unreachable code");
 st[1] = MAP(st[1], function(def){
 if (def[1] && !options.no_warnings)
 warn_unreachable([ "assign", true, [ "name", def[0] ], def[1] ]);
 return [ def[0] ];
 });
 a.push(st);
 }
 else if (!options.no_warnings)
 warn_unreachable(st);
 }
 else {//当前作用域已经到了return语句了那后边的可以考虑压缩忽略掉
 a.push(st);
 if (member(st[0], [ "return", "throw", "break", "continue" ]))
 has_quit = true;
 }
 });
 return a;
 })([]);

 //当调用 ast_squeeze() 将会合并多个语句块为一个语句块，如 "a=10; b=20; foo()" 将被转换为 "a=10,b=20,foo()"
 //make_seqs默认为true
 //命令参数"--no-seqs"可以让make_seqs = false
 if (options.make_seqs) statements = (function(a, prev) {
 statements.forEach(function(cur){
 //把连续的表达式语句合并成一个逗号表达式。
 //stat;stat;stat; => stat,stat,stat;
 if (prev && prev[0] == "stat" && cur[0] == "stat") {
 prev[1] = [ "seq", prev[1], cur[1] ];
 } else {
 a.push(cur);
 prev = cur;
 }
 });
 //块的最后一句是：
 //
 /*
 stat;
 return A;
 可以优化成为
 return stat, A;
 */
 if (a.length >= 2
 && a[a.length-2][0] == "stat"
 && (a[a.length-1][0] == "return" || a[a.length-1][0] == "throw")
 && a[a.length-1][1])
 {
 a.splice(a.length - 2, 2,
 [ a[a.length-1][0],
 [ "seq", a[a.length-2][1], a[a.length-1][1] ]]);
 }
 return a;
 })([]);

 // this increases jQuery by 1K.Probably not such a good idea after all..
 // part of this is done in prepare_ifs anyway.
 // if (block_type == "lambda") statements = (function(i, a, stat){
 // while (i < statements.length) {
 // stat = statements;
 // if (stat == "if" && !stat) {
 // if (stat == "return" && stat == null) {
 // a.push(make_if(negate(stat), [ "block", statements.slice(i) ]));
 // break;
 // }
 // var last = last_stat(stat);
 // if (last == "return" && last == null) {
 // a.push(make_if(stat, [ "block", stat.slice(0, -1) ], [ "block", statements.slice(i) ]));
 // break;
 // }
 // }
 // a.push(stat);
 // }
 // return a;
 // })(0, []);

 return statements;
};

//对if进行优化
function make_if(c, t, e) {
//if (c) {t} else{e}
//尝试对c这个表达式化简~
 return when_constant(c, function(ast, val){
 //如果c最后可以化简成表达式
 //如果val == true || false之类的
 //那就有可以去掉else或者then语句了
 //@optimize
 if (val) {
 /*
 if (true){
A();
 }else{
B();
 }
 化简成：A();
 */
 t = walk(t);
 warn_unreachable(e);
 return t || [ "block" ];
 } else {
 /*
 if (false){
A();
 }else{
B();
 }
 化简成：B();
 */
 e = walk(e);
 warn_unreachable(t);
 return e || [ "block" ];
 }
 }, function() {
 //c没法化简那就只能走make_real_if来压缩if树
 return make_real_if(c, t, e);
 });
};

//if (c) {t;} else { e; return ; }
//优化成 if (!c) { e;return; } t;
function abort_else(c, t, e) {
 var ret = [ [ "if", negate(c), e ] ];
 if (t[0] == "block") {
 if (t[1]) ret = ret.concat(t[1]);
 } else {
 ret.push(t);
 }
 return walk([ "block", ret ]);
};

//压缩if树枝
function make_real_if(c, t, e) {
//if (c) { t } else {e}
 c = walk(c);
 t = walk(t);
 e = walk(e);

 //if (cond()) {} else{}
 //可以化简成 cond()
 if (empty(e) && empty(t))
 return [ "stat", c ];

 if (empty(t)) {
 //if (cond()) {} else{ B() }
 //可以化简成 if (!cond()) { B() }
 c = negate(c);
 t = e;
 e = null;
 } else if (empty(e)) {
 //if (cond()) { A() } else{ }
 //可以化简成 if (cond()) { A() }
 e = null;
 } else {
 // if we have both else and then, maybe it makes sense to switch them?
 (function(){
 var a = gen_code(c);
 var n = negate(c);//对条件c求反
 var b = gen_code(n);
 //尝试把条件求反，如果得到的表达式更短
 //那么反转if跟else块
 if (b.length < a.length) {
 var tmp = t;
 t = e;
 e = tmp;
 c = n;
 }
 })();
 }

 //按照目前得到的AST树枝是这样：
 var ret = [ "if", c, t, e ];

 //考虑分块操作两个句子的情况，只有一个句子的话丢给make_conditional去考虑

 if (t[0] == "if" && empty(t[3]) && empty(e)) {
 //嵌套IF的压缩
 //if (c1) { if (c2) { A() } } else{} 尝试化成这样的AST： if (c1 && c2) { A()}
 //看看哪个AST生成的代码短，谁短用谁。
 ret = best_of(ret, walk([ "if", [ "binary", "&&", c, t[1] ], t[2] ]));
 }
 else if (t[0] == "stat") {//如果if分支列表是一个语句
 if (e) {
 if (e[0] == "stat")
 //else也是一个语句，那就搞成条件表达式
 ret = best_of(ret, [ "stat", make_conditional(c, t[1], e[1]) ]);
 else if (aborts(e))//如果else最后有return等跳转控制的关键字
 ret = abort_else(c, t, e);
 }
 else {//else为空的情况，也搞成条件表达式
 ret = best_of(ret, [ "stat", make_conditional(c, t[1]) ]);
 }
 }
 else if (e && t[0] == e[0] && (t[0] == "return" || t[0] == "throw") && t[1] && e[1]) {
 //if (c) { return A(); } else { return B(); }
 //优化成：return c ? A() : B();
 ret = best_of(ret, [ t[0], make_conditional(c, t[1], e[1] ) ]);
 }
 else if (e && aborts(t)) {
 //看到prepare_ifs做的操作被这里还原回去了~
 ret = [ [ "if", c, t ] ];
 if (e[0] == "block") {
 if (e[1]) ret = ret.concat(e[1]);
 }
 else {
 ret.push(e);
 }
 ret = walk([ "block", ret ]);
 }
 else if (t && aborts(e)) {
 ret = abort_else(c, t, e);
 }
 return ret;
};

function _do_while(cond, body) {
 return when_constant(cond, function(cond, val){
 if (!val) {//while(false){}变成空语句
 warn_unreachable(body);
 return [ "block" ];
 } else {//while(true){}变成for(;;){} 缩短4个字符！
 return [ "for", null, null, null, walk(body) ];
 }
 });
};

//遍历AST树此时遍历名已经混淆过~
return w.with_walkers({
//对于表达式 expr 的优化
 "sub": function(expr, subscript) {
 if (subscript[0] == "string") {
 var name = subscript[1];
 if (is_identifier(name))
 //a["b"] ==> a.b
 //这样可以省去3个字符
 return [ "dot", walk(expr), name ];
 else if (/^*$/.test(name) || name === "0")
 //a => a
 //表达式可能是八进制的，化成10禁止会更短
 return [ "sub", walk(expr), [ "num", parseInt(name, 10) ] ];
 }
 },
 "if": make_if,
 "toplevel": function(body) {
 return [ "toplevel", tighten(body) ];
 },
 "switch": function(expr, body) {
 var last = body.length - 1;
 return [ "switch", walk(expr), MAP(body, function(branch, i){
 var block = tighten(branch[1]);
 if (i == last && block.length > 0) {
 //最后一个case分支，最后一句的break;可以去掉
 //留意break labelName;这种是不能省略的
 var node = block[block.length - 1];
 if (node[0] == "break" && !node[1])
 block.pop();//忽略最后一句break;
 }
 return [ branch[0] ? walk(branch[0]) : null, block ];
 }) ];
 },
 "function": _lambda,
 "defun": _lambda,
 "block": function(body) {
 if (body) return rmblock([ "block", tighten(body) ]);
 },
 "binary": function(op, left, right) {
 return when_constant([ "binary", op, walk(left), walk(right) ], function yes(c){
 return best_of(walk(c), this);
 }, function no() {
 return function(){
 if(op != "==" && op != "!=") return;
 //只有==跟!=才压缩
 var l = walk(left), r = walk(right);

 //!1 == right
 if(l && l[0] == "unary-prefix" && l[1] == "!" && l[2][0] == "num")
 left = ['num', +!l[2][1]];

 //left == !2
 else if (r && r[0] == "unary-prefix" && r[1] == "!" && r[2][0] == "num")
 right = ['num', +!r[2][1]];

 return ["binary", op, left, right];
 }() || this;
 });
 },
 "conditional": function(c, t, e) {
 return make_conditional(walk(c), walk(t), walk(e));
 },
 "try": function(t, c, f) {
 return [
 "try",
 tighten(t),
 c != null ? [ c[0], tighten(c[1]) ] : null,
 f != null ? tighten(f) : null
 ];
 },
 "unary-prefix": function(op, expr) {
 expr = walk(expr);
 var ret = [ "unary-prefix", op, expr ];
 if (op == "!")//!(a>=b) 优化成 a>', '<<', '>>>', '|', '^', '&' ];
 //赋值语句一般是+= -= ，所以语法分析时候解析出来的op是去掉=的结果，
 //但是如果是a = 1的话,op不好用一个空字符串来表示，所以用了true
 //a = a + b; 优化成为 a += b
 if (op === true && lvalue[0] === "name" && rvalue[0] === "binary" &&
 ~okOps.indexOf(rvalue[1]) && rvalue[2][0] === "name" &&
 rvalue[2][1] === lvalue[1]) {
 //原本是：["assign", true, ["name", "a"], ["binary", ["name", "a"], ["name", "b"]]]
 //压缩成：["assign", "+", ["name", "a"], ["name", "b"]]
 return [ this[0], rvalue[1], lvalue, rvalue[3] ]
 }
 return [ this[0], op, lvalue, rvalue ];
 },
 "call": function(expr, args) {
 expr = walk(expr);
 //把"string".toString();替换成"string"
 if (options.unsafe && expr[0] == "dot" && expr[1][0] == "string" && expr[2] == "toString") {
 return expr[1];
 }
 return [ this[0], expr,MAP(args, walk) ];
 },
 "num": function (num) {
 if (!isFinite(num))//如果是无穷大或者NaN
 //Infinity => 1/0
 //-Infinity => -1/0
 //NaN => 0/0
 return [ "binary", "/", num === 1 / 0
 ? [ "num", 1 ] : num === -1 / 0
 ? [ "unary-prefix", "-", [ "num", 1 ] ]
 : [ "num", 0 ], [ "num", 0 ] ];

 return [ this[0], num ];
 }
}, function() {
//遍历之前先处理一下IF
//这里还重复处理两次？@unkowned
 return walk(prepare_ifs(walk(prepare_ifs(ast))));
});
};

//去除重复的指示性字符串，例如
/*
function (){
"use strict";
function (){
"use strict";
}
}
压缩成：

function (){
"use strict";
function (){
}
}
*/
function squeeze_2(ast, options) {
var w = ast_walker(), walk = w.walk, scope;
function with_scope(s, cont) {
 var save = scope, ret;
 scope = s;
 ret = cont();
 scope = save;
 return ret;
};
function lambda(name, args, body) {
 return [ this[0], name, args, with_scope(body.scope, curry(MAP, body, walk)) ];
};
return w.with_walkers({
 "directive": function(dir) {
 if (scope.active_directive(dir))
 return [ "block" ];
 scope.directives.push(dir);
 },
 "toplevel": function(body) {
 return [ this[0], with_scope(this.scope, curry(MAP, body, walk)) ];
 },
 "function": lambda,
 "defun": lambda
}, function(){
 return walk(ast_add_scope(ast));
});
};</code></pre></div><div class="topic-firstfloor-additional" style="margin-top: 10px; margin-bottom: 10px; color: rgb(51, 51, 51); font-family: "Microsoft Yahei", 微软雅黑, "Helvetica Neue", adobe雅黑, "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 12px; line-height: 18px;"></div><div class="user-actions" style="color: rgb(153, 153, 153); padding: 12px 5px; margin-top: 10px; border-top-width: 1px; border-top-style: solid; border-top-color: rgb(226, 226, 226); font-family: "Microsoft Yahei", 微软雅黑, "Helvetica Neue", adobe雅黑, "helvetica neue", tahoma, "hiragino sans gb", stheiti, "wenquanyi micro hei", 微软雅黑, 宋体, sans-serif; font-size: 12px; line-height: 18px;"><div class="faved-user" style="position: absolute; top: -26px; right: 0px;"><a href="http://div.io/user/admin" class="avatar" style="text-decoration: none; color: rgb(38, 159, 63);"><img src="http://div.io/uploads/avatar/223_s.jpg" alt="chromefans" style="width: 24px; height: 24px; border-radius: 24px;"></a> <a href="http://div.io/user/vip" class="avatar" style="text-decoration: none; color: rgb(38, 159, 63);"><img src="http://div.io/uploads/avatar/263_s.png" alt="GZShi" style="width: 24px; height: 24px; border-radius: 24px;"></a> <a href="http://div.io/user/div" class="avatar" style="text-decoration: none; color: rgb(38, 159, 63);"><img src="http://div.io/uploads/avatar/514_s.png" alt="树上有云" style="width: 24px; height: 24px; border-radius: 24px;"></a> 3 人关注了该主题</div><div> </div><span class="fa fa-weibo" style="display: inline-block; font-stretch: normal; line-height: 1; font-family: FontAwesome; font-size: 14px; text-rendering: auto; -webkit-font-smoothing: antialiased; transform: translate(0px, 0px); color: rgb(165, 165, 165);"></div>

页: [1]

守望者--AIR技术交流's Archiver

Javascript代码压缩细节