分享一个自定义的console类 让你不再纠结JS中的调试代码的兼容

问题的产生

在写JS的过程中，为了调试我们常常会写很多 console.log、console.info、console.group、console.warn、console.error代码来查看JS的运行情况，但发布时又因为IE不支持console，又要去掉这些代码，一不小心就会出错。

本文分享自己昨晚写的一个console类来试图解决这一问题。当然，更好的做法是把测试代码分开写，那样就不会有这个问题。

解决思路

如何解决IE下不兼容的问题呢，那就是我们自己定义一个console类来覆盖浏览器提供的console功能，这样只要在页面中引用此JS文件就可以了。

另外，此类还提供了查看输出的调试信息功能，console 定义了哪些功能呢，我们可以在这里看到：http://getfirebug.com/wiki/index.php/Console_API，我们可以看到这里提供了很多方法，我们常用的有 console.log、console.info、console.group、console.warn、console.error、console.profile、console.time，最后两个是分析代码性能的，比较复杂，本文没有实现。
代码解析

第一步，当然是搭一个结构，覆盖浏览器(firebug、chrome)提供的console功能，这样直接引用此JS文件即可保证浏览器(主要是IE)中不出错：

console var console={ 
assert:function(){ 
}, 
clear:function(){ 
}, 
count:function(){ 
}, 
debug:function(){ 
}, 
dir:function(){ 
}, 
dirxml:function(){ 
}, 
error:function(){ 
}, 
exception:function(){ 
}, 
group:function(name){ 
}, 
groupCollapsed:function(){ 
}, 
groupEnd:function(){ 
}, 
info:function(){ 
}, 
log:function(){ 
}, 
memoryProfile:function(){ 
}, 
memoryProfileEnd:function(){ 
}, 
profile:function(){ 
}, 
profileEnd:function(){ 
}, 
table:function(){ 
}, 
time:function(){ 
}, 
timeEnd:function(){ 
}, 
timeStamp:function(){ 
}, 
trace:function(){ 
}, 
warn:function(){ 
} 
};

第二步，实现 console.log方法。在所实现的几个方法中这个是最复杂的。

从firebug的API中我们可以看到，console.log不仅仅可以输出信息，还提供了类似 string.Format的功能，直接引用原文如下：

Here is the complete set of patterns that you may use for string substitution:

Pattern	Type
%s	String
%d, %i	Integer (numeric formatting is not yet supported)
%f	Floating point number (numeric formatting is not yet supported)
%o	Object hyperlink
%c	Style formatting

其中的%c比较特殊，是给输出添加样式的，比如我们在firebug中这样写：

console.log('%cTest output', 'color:white; background-color:blue');

运行后的结果是这样的：

这里%c也可以跟 %s、%d等混用。

所以，在代码中我直接用replace进行替换，由于JS中的replace默认只替换第一个匹配项，这里刚好，代码如下：

var args=Array.prototype.slice.call(arguments); 
if(args.length>1){ 
var i=1,hasstyle=false; 
if(args[0].indexOf("%c")==0){ 
args[0]=args[0].replace(/%c/,""); 
i=2; 
hasstyle=true; 
} 
for(;i<args.length;i++){ 
if(/%s|%d|%i|%o/.test(args[0])){ 
args[0]=args[0].replace(/%s|%d|%i|%o/,args[i]); 
} 
else{ 
break; 
} 
} 
if(i<args.length){ 
args[0]=args[0]+" "+args.slice(i).join(" "); 
} 
if(hasstyle){ 
consoleHelper.showlog(args[0],args[1]); 
} 
else{ 
consoleHelper.showlog(args[0]); 
} 
} 
else if(args.length==1){ 
if(arguments[0] instanceof Array){ 
consoleHelper.showlog("["+args[0]+"]"); 
} 
else if(arguments[0] instanceof Function){ 
consoleHelper.showlog(args[0],null,"console_log_function"); 
} 
else{ 
consoleHelper.showlog(args[0]); 
} 
} 
else{ 
consoleHelper.showlog(""); 
}

由于console.log可以接受多个参数，且个数不确定，所以这里直接没有写形参。对于%c虽然firebug中写在中间也是有效的，这里为了简单直接只对写在开头的有效。代码中先把参数转换为数组，然后对数组进行分情况处理。

当参数个数大于1时，对后面的参数用replace进行替换，然后把剩下的参数连接(join)起来进行输出。

当参数个数为1时，还要分两种情况，一是数组，二是方法。对于数组，按firebug中的格式，在两端加中括号，对于函数，把字的颜色变为绿色

当参数个数为0时，直接输出空字符串

后面的consoleHelper.showlog是为了输出方便另外写的一个方法，在这个方法中把各种调试信息的结果显示在页面上的一个div(如果存在)中。

其他几个方法的思路跟这个差不多，只是样式不同，功能比这个简单，直接把参数连接起来输出即可。

整个console类代码如下：

console全部代码 var console={ 
assert:function(){ 
}, 
clear:function(){ 
}, 
count:function(){ 
}, 
debug:function(){ 
}, 
dir:function(){ 
}, 
dirxml:function(){ 
}, 
error:function(){ 
var args=Array.prototype.slice.call(arguments); 
consoleHelper.showerror(args.join(" ")); 
}, 
exception:function(){ 
}, 
group:function(name){ 
consoleHelper.showgroup(name); 
}, 
groupCollapsed:function(){ 
}, 
groupEnd:function(){ 
}, 
info:function(){ 
var args=Array.prototype.slice.call(arguments); 
if(args.length==1){ 
if(arguments[0] instanceof Array){ 
consoleHelper.showinfo("["+args[0]+"]"); 
} 
else if(arguments[0] instanceof Function){ 
consoleHelper.showinfo(args[0],"console_log_function"); 
} 
else{ 
consoleHelper.showinfo(args[0]); 
} 
} 
else{ 
consoleHelper.showinfo(args.join(" ")); 
} 
}, 
log:function(){ 
var args=Array.prototype.slice.call(arguments); 
if(args.length>1){ 
var i=1,hasstyle=false; 
if(args[0].indexOf("%c")==0){ 
args[0]=args[0].replace(/%c/,""); 
i=2; 
hasstyle=true; 
} 
for(;i<args.length;i++){ 
if(/%s|%d|%i|%o/.test(args[0])){ 
args[0]=args[0].replace(/%s|%d|%i|%o/,args[i]); 
} 
else{ 
break; 
} 
} 
if(i<args.length){ 
args[0]=args[0]+" "+args.slice(i).join(" "); 
} 
if(hasstyle){ 
consoleHelper.showlog(args[0],args[1]); 
} 
else{ 
consoleHelper.showlog(args[0]); 
} 
} 
else if(args.length==1){ 
if(arguments[0] instanceof Array){ 
consoleHelper.showlog("["+args[0]+"]"); 
} 
else if(arguments[0] instanceof Function){ 
consoleHelper.showlog(args[0],null,"console_log_function"); 
} 
else{ 
consoleHelper.showlog(args[0]); 
} 
} 
else{ 
consoleHelper.showlog(""); 
} 
}, 
memoryProfile:function(){ 
}, 
memoryProfileEnd:function(){ 
}, 
profile:function(){ 
}, 
profileEnd:function(){ 
}, 
table:function(){ 
}, 
time:function(){ 
}, 
timeEnd:function(){ 
}, 
timeStamp:function(){ 
}, 
trace:function(){ 
}, 
warn:function(){ 
var args=Array.prototype.slice.call(arguments); 
if(args.length==1){ 
if(arguments[0] instanceof Array){ 
consoleHelper.showwarn("["+args[0]+"]"); 
} 
else if(arguments[0] instanceof Function){ 
consoleHelper.showwarn(args[0],"console_log_function"); 
} 
else{ 
consoleHelper.showwarn(args[0]); 
} 
} 
else{ 
consoleHelper.showwarn(args.join(" ")); 
} 
} 
};

consoleHelper代码如下：

var consoleHelper={ 
showlog:function(val,style,cla){ 
if(cla){ 
cla="console_log "+cla; 
} 
else{ 
cla="console_log"; 
} 
this.show(val,style,cla); 
}, 
showinfo:function(val,cla){ 
if(cla){ 
cla="console_info "+cla; 
} 
else{ 
cla="console_info"; 
} 
this.show(val,null,cla); 
}, 
showwarn:function(val,cla){ 
if(cla){ 
cla="console_warn "+cla; 
} 
else{ 
cla="console_warn"; 
} 
this.show(val,null,cla); 
}, 
showerror:function(val){ 
this.show(val,null,"console_error"); 
}, 
showgroup:function(val){ 
if(!val){ 
val=""; 
} 
this.show(val+":",null,"console_group"); 
}, 
show:function(val,style,cla){ 
if(document.getElementById("showconsole")){ 
var div=document.createElement("div"); 
if(div.setAttribute){ 
if(style){ 
div.setAttribute("style",style); 
} 
} 
else{ 
if(style){ 
div=document.createElement("<div style="+style+">"); 
} 
} 
if(cla){ 
div.className=cla; 
} 
var oText=document.createTextNode(val); 
div.appendChild(oText); 
document.getElementById("showconsole").appendChild(div); 
} 
} 
};

注：如果想在页面中看到调试信息，直接在页面上添加一个id 为 showconsole 的隐藏的div即可。

样式(尽量跟FireBug保持一致)：

.console_log{ 
border:1px solid #CCC; 
color:#333; 
padding:0px 5px; 
min-height:24px; 
line-height:24px; 
margin-bottom:-1px; 
} 
.console_info{ 
border:1px solid #CCC; 
color:#333; 
padding:0px 5px; 
min-height:24px; 
line-height:24px; 
margin-bottom:-1px; 
background: url("data:image/png;base64,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") no-repeat scroll 0 1px #EBF5FF; 
padding-left:30px; 
} 
.console_warn{ 
border:1px solid #CCC; 
color:#333; 
padding:0px 5px; 
min-height:24px; 
line-height:24px; 
margin-bottom:-1px; 
background: url("data:image/png;base64,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") no-repeat scroll 0 1px #FFFFC8; 
padding-left:30px; 
} 
.console_error{ 
border:1px solid #CCC; 
color:#FF0000; 
padding:0px 5px; 
min-height:24px; 
line-height:24px; 
margin-bottom:-1px; 
background: url("data:image/png;base64,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") no-repeat scroll 0 1px #FFEBEB; 
padding-left:30px; 
} 
.console_group{ 
margin-top:20px; 
font-size:16px; 
font-weight:bolder; 
} 
.console_log_function{ 
color:green; 
}

这里为了演示方便，三个小图标直接用的是base64格式的图片，就是上面代码中的三个长字符串，大家用时可以换成图片地址。
完整代码：

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<!DOCTYPE html> 
<html> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> 
<title>自定义console</title> 
<style type="text/css"> 
.console_log{ 
border:1px solid #CCC; 
color:#333; 
padding:0px 5px; 
min-height:24px; 
line-height:24px; 
margin-bottom:-1px; 
} 
.console_info{ 
border:1px solid #CCC; 
color:#333; 
padding:0px 5px; 
min-height:24px; 
line-height:24px; 
margin-bottom:-1px; 
background: url("data:image/png;base64,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") no-repeat scroll 0 1px #EBF5FF; 
padding-left:30px; 
} 
.console_warn{ 
border:1px solid #CCC; 
color:#333; 
padding:0px 5px; 
min-height:24px; 
line-height:24px; 
margin-bottom:-1px; 
background: url("data:image/png;base64,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") no-repeat scroll 0 1px #FFFFC8; 
padding-left:30px; 
} 
.console_error{ 
border:1px solid #CCC; 
color:#FF0000; 
padding:0px 5px; 
min-height:24px; 
line-height:24px; 
margin-bottom:-1px; 
background: url("data:image/png;base64,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") no-repeat scroll 0 1px #FFEBEB; 
padding-left:30px; 
} 
.console_group{ 
margin-top:20px; 
font-size:16px; 
font-weight:bolder; 
} 
.console_log_function{ 
color:green; 
} 
</style> 
<script type="text/javascript"> 
var console={ 
assert:function(){ 
}, 
clear:function(){ 
}, 
count:function(){ 
}, 
debug:function(){ 
}, 
dir:function(){ 
}, 
dirxml:function(){ 
}, 
error:function(){ 
var args=Array.prototype.slice.call(arguments); 
consoleHelper.showerror(args.join(" ")); 
}, 
exception:function(){ 
}, 
group:function(name){ 
consoleHelper.showgroup(name); 
}, 
groupCollapsed:function(){ 
}, 
groupEnd:function(){ 
}, 
info:function(){ 
var args=Array.prototype.slice.call(arguments); 
if(args.length==1){ 
if(arguments[0] instanceof Array){ 
consoleHelper.showinfo("["+args[0]+"]"); 
} 
else if(arguments[0] instanceof Function){ 
consoleHelper.showinfo(args[0],"console_log_function"); 
} 
else{ 
consoleHelper.showinfo(args[0]); 
} 
} 
else{ 
consoleHelper.showinfo(args.join(" ")); 
} 
}, 
log:function(){ 
var args=Array.prototype.slice.call(arguments); 
if(args.length>1){ 
var i=1,hasstyle=false; 
if(args[0].indexOf("%c")==0){ 
args[0]=args[0].replace(/%c/,""); 
i=2; 
hasstyle=true; 
} 
for(;i<args.length;i++){ 
if(/%s|%d|%i|%o/.test(args[0])) { 
args[0]=args[0].replace(/%s|%d|%i|%o/,args[i]); 
} 
else{ 
break; 
} 
} 
if(i<args.length){ 
args[0]=args[0]+" "+args.slice(i).join(" "); 
} 
if(hasstyle){ 
consoleHelper.showlog(args[0],args[1]); 
} 
else{ 
consoleHelper.showlog(args[0]); 
} 
} 
else if(args.length==1){ 
if(arguments[0] instanceof Array){ 
consoleHelper.showlog("["+args[0]+"]"); 
} 
else if(arguments[0] instanceof Function){ 
consoleHelper.showlog(args[0],null,"console_log_function"); 
} 
else{ 
consoleHelper.showlog(args[0]); 
} 
} 
else{ 
consoleHelper.showlog(""); 
} 
}, 
memoryProfile:function(){ 
}, 
memoryProfileEnd:function(){ 
}, 
profile:function(){ 
}, 
profileEnd:function(){ 
}, 
table:function(){ 
}, 
time:function(){ 
}, 
timeEnd:function(){ 
}, 
timeStamp:function(){ 
}, 
trace:function(){ 
}, 
warn:function(){ 
var args=Array.prototype.slice.call(arguments); 
if(args.length==1){ 
if(arguments[0] instanceof Array){ 
consoleHelper.showwarn("["+args[0]+"]"); 
} 
else if(arguments[0] instanceof Function){ 
consoleHelper.showwarn(args[0],"console_log_function"); 
} 
else{ 
consoleHelper.showwarn(args[0]); 
} 
} 
else{ 
consoleHelper.showwarn(args.join(" ")); 
} 
} 
}; 
var consoleHelper={ 
showlog:function(val,style,cla){ 
if(cla){ 
cla="console_log "+cla; 
} 
else{ 
cla="console_log"; 
} 
this.show(val,style,cla); 
}, 
showinfo:function(val,cla){ 
if(cla){ 
cla="console_info "+cla; 
} 
else{ 
cla="console_info"; 
} 
this.show(val,null,cla); 
}, 
showwarn:function(val,cla){ 
if(cla){ 
cla="console_warn "+cla; 
} 
else{ 
cla="console_warn"; 
} 
this.show(val,null,cla); 
}, 
showerror:function(val){ 
this.show(val,null,"console_error"); 
}, 
showgroup:function(val){ 
if(!val){ 
val=""; 
} 
this.show(val+":",null,"console_group"); 
}, 
show:function(val,style,cla){ 
if(document.getElementById("showconsole")){ 
var div=document.createElement("div"); 
if(div.setAttribute){ 
if(style){ 
div.setAttribute("style",style); 
} 
} 
else{ 
if(style){ 
div=document.createElement("<div style="+style+">"); 
} 
} 
if(cla){ 
div.className=cla; 
} 
var oText=document.createTextNode(val); 
div.appendChild(oText); 
document.getElementById("showconsole").appendChild(div); 
} 
} 
}; 
window.onload=function(){ 
console.group("log"); 
console.log('%c a %s This is red text on a green background','color:red; background-color:#EEE'); 
console.log("The %%s jumped over %d tall buildings",1, "abc",1); 
console.log("I am %s and I have:", "abc", "bcd","cde"); 
console.log("abc",1); 
console.log([1,2,3,4,5]); 
console.log(); 
console.log(test); 
console.group("info"); 
console.info('%c a %s This is red text on a green background','color:red; background-color:#EEE'); 
console.info("The %%s jumped over %d tall buildings",1, "abc",1); 
console.info("I am %s and I have:", "abc", "bcd","cde"); 
console.info("abc",1); 
console.info([1,2,3,4,5]); 
console.info(); 
console.info(test); 
console.group("warn"); 
console.warn('%c a %s This is red text on a green background','color:red; background-color:#EEE'); 
console.warn("The %%s jumped over %d tall buildings",1, "abc",1); 
console.warn("I am %s and I have:", "abc", "bcd","cde"); 
console.warn("abc",1); 
console.warn([1,2,3,4,5]); 
console.warn(); 
console.warn(test); 
console.group("error"); 
console.error('%c a %s This is red text on a green background','color:red; background-color:#EEE'); 
console.error("The %%s jumped over %d tall buildings",1, "abc",1); 
console.error("I am %s and I have:", "abc", "bcd","cde"); 
console.error("abc",1); 
console.error([1,2,3,4,5]); 
console.error(test); 
} 
function test(){ 
alert("abc"); 
alert("abc"); 
alert("abc"); 
alert("abc"); 
alert("abc"); 
alert("abc"); 
alert("abc"); 
alert("abc");alert("abc"); 
} 
</script> 
</head> 
<body> 
<h1>自定义console(Artwl.cnblogs.com)</h1> 
<div id="showconsole"></div> 
</body> 
</html>

小结

写这个JS一方面是工作中有这方面的需求，另外也是因为在博问中看到有人问 JavaScript中如何获得console.log的值？ ，前段时间有个国外学编程网站可以把console.log的结果直接显示在页面上，不知道是不是用了本文类似的方案。

欢迎大家留言讨论。
作者：Artwl