JavaScript深度比较Object、Array与Function对象相等性的实现

JavaScript深度比较Object、Array与Function对象相等性的实现

在迭代过程中需特别注意，对象或数组内的元素可能是任意值。除了原始类型值、object和array外，这些值还可能是一个方法、一个DOM对象或者window对象。部分引用类型无法直接进行迭代，因此需要引入分支判断逻辑，具体代码如下：

 
function compare(a,b){
var
pt = /undefined|number|string|boolean/,
fn = /^(function\s*)(\w*\b)/,
cr = "constructor",
cn = "childNodes",
pn = "parentNode",
ce = arguments.callee;
if(pt.test(typeof a) || pt.test(typeof b) || a === null || b === null){
return a === b || (isNaN(a) && isNaN(b)); //为了方便，此处假定NaN == NaN
} 
if(a[cr] !== b[cr]){
return false;
} 
switch(a[cr]){
case Date : {
return a.valueOf() === b.valueOf();
}; 
case Function : {
return a.toString().replace(fn,'$1') === b.toString().replace(fn,'$1'); //硬编码中声明函数的方式会影响到toString的结果，因此用正则进行格式化
}; 
case Array : {
if(a.length !== b.length){
return false;
} 
for(var i=0;i<a.length;i++){
if(!ce(a[i],b[i])){
return false;
} 
} 
break;
}; 
default : {
var alen = 0, blen = 0, d;
if(a === b){
return true;
} 
if(a[cn] || a[pn] || b[cn] || b[pn]){
return a === b;
} 
for(d in a){
alen++ ;
} 
for(d in b){
blen++;
} 
if(alen !== blen){
return false;
} 
for(d in a){
if(!ce(a[d],b[d])){
return false;
} 
} 
break;
}; 
} 
return true;
} 
console.log(compare({},{a:1})); //false
console.log(compare({a:1},{b:2})); //false
console.log(compare({b:2,a:1},{a:1,b:2})); //true
console.log(compare({a:function(){return false;},b:2},{a:function(){return false;},b:2})); //true
console.log(compare([],[])); //true
console.log(compare([2,1],[1,2])); //false
console.log(compare(function(){alert(1)},function(){})); //false
console.log(compare(function aaa(){alert(1)},function(){alert(1)})); //true
console.log(compare(document.getElementsByTagName("a")[0],document.getElementsByTagName("a")[1])); //false
console.log(compare(document.getElementsByTagName("a")[0],document.getElementsByTagName("a")[0])); //true