克隆javascript对象的三个方法小结

function clone(obj){ 
var o; 
switch(typeof obj){ 
case 'undefined': break; 
case 'string' : o = obj + '';break; 
case 'number' : o = obj - 0;break; 
case 'boolean' : o = obj;break; 
case 'object' : 
if(obj === null){ 
o = null; 
}else{ 
if(obj instanceof Array){ 
o = []; 
for(var i = 0, len = obj.length; i < len; i++){ 
o.push(clone(obj[i])); 
} 
}else{ 
o = {}; 
for(var k in obj){ 
o[k] = clone(obj[k]); 
} 
} 
} 
break; 
default: 
o = obj;break; 
} 
return o; 
}

function clone2(obj){ 
var o, obj; 
if (obj.constructor == Object){ 
o = new obj.constructor(); 
}else{ 
o = new obj.constructor(obj.valueOf()); 
} 
for(var key in obj){ 
if ( o[key] != obj[key] ){ 
if ( typeof(obj[key]) == 'object' ){ 
o[key] = clone2(obj[key]); 
}else{ 
o[key] = obj[key]; 
} 
} 
} 
o.toString = obj.toString; 
o.valueOf = obj.valueOf; 
return o; 
}

function clone3(obj){ 
function Clone(){} 
Clone.prototype = obj; 
var o = new Clone(); 
for(var a in o){ 
if(typeof o[a] == "object") { 
o[a] = clone3(o[a]); 
} 
} 
return o; 
}