上次 我们谈到Javascript 中 浅拷贝与深拷贝的实现..
这回我们看看如何实现判断两个对像的内容是否相等.
这里有一个克隆结果原则是针对Java语言的,当然JavaScript也可以胜任.
克隆满足的条件
clone()方法将对象复制了一份并返还给调用者。所谓“复制”的含义与clone()方法是怎么实现的有关。一般而言，clone()方法满足以下的描述：
第一、对任何的对象x，都有：x.clone() != x；换言之，克隆对象与原对象不是同一个对象；
第二、对任何的对象x，都有：x.clone().getClass == x.getClass()，换言之，克隆对象与原对象的类型一样；在Javascript getClass 就相当于constructor
第三、如果对象x的equals()方法是定义恰当的话，那么 x.clone().equals(x)也应当是成立的。
在Java语言的API中，凡是提供了clone()方法的类，都满足上面的这些这些条件。Java语言的设计师在设计自己的clone()方法是，也应当遵守这三个条件。
第三条为可选,不必强制实现的,意思是说只要编制得当,也可以实现.
1. 我们还拿上次的列子看一下:
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<META NAME="Generator" CONTENT="Wawa Editor 1.0">
<META NAME="Author" CONTENT="八神奄">
<META NAME="Keywords" CONTENT="Javascript,Java,XML,XSLT,ASP,VBScript,ASP .net,C#,C++,Database">
<META NAME="Description" CONTENT="不及格的程序员,无所不在">
</HEAD>
<BODY>
<SCRIPT LANGUAGE="JavaScript">
<!--
function Object.prototype.equals(obj){
if(this == obj)return true;
if(typeof(obj)=="undefined"||obj==null||typeof(obj)!="object")return false;
var length = 0; var length1=0;
for(var ele in this) length++;for(var ele in obj) length1++;
if(length!=length1) return false;
if(obj.constructor==this.constructor){
for(var ele in this){
if(typeof(this[ele])=="object") {if(!this[ele].equals(obj[ele]))return false;}
else if(typeof(this[ele])=="function"){if(!this[ele].toString().equals(obj[ele].toString())) return false;}
else if(this[ele]!=obj[ele]) return false;
}
return true;
}
return false;
}
function String.prototype.equals(str){
if(this==str)return true;
return false;
}
function Function.prototype.equals(func){
if(this.toString().equals(func.toString()))return true;
return false;
}
function Boolean.prototype.equals(bool){
if(this==bool)return true;
if (bool instanceof Boolean){
return this.toString().equals(bool.toString());
}
return false;
}
function Object.prototype.clone(){
var newObj = new Object();
for(elements in this){
newObj[elements] = this[elements];
}
return newObj;
}
function Object.prototype.cloneAll(){
function clonePrototype(){}
clonePrototype.prototype = this;
var obj = new clonePrototype();
for(var ele in obj){
if(typeof(obj[ele])=="object") obj[ele] = obj[ele].cloneAll();
}
return obj;
}
var obj1 = new Object();
obj1.Team = "First";
obj1.Powers = new Array("Iori","Kyo");
obj1.msg = function(){alert()};
obj1.winner = new Object();
obj1.winner.name = obj1.Powers[0];
obj1.winner.age = 23;
obj1.winner.from = "Japan"
var obj1_clone = obj1.cloneAll();
alert("刚刚克隆之后,对比结果为: "+obj1_clone.equals(obj1))
obj1_clone.Team = "Second";
obj1_clone.Powers = new Array("Jimmy","Anndy");
obj1_clone.winner.name = obj1_clone.Powers[1];
obj1_clone.winner.age = 22;
obj1_clone.winner.from = "USA";
alert("修改过被克隆对像属性之后的对比结果: "+obj1_clone.equals(obj1))
alert("是否符合上面提到的第二条原则呢,结果为: "+(obj1_clone.constructor==obj1.constructor))
msg = "2003界拳皇单打独斗杯,拳皇挑战赛: \n\n A组 对战形式:\n\n"
msg += obj1.Team+" 组 ,人员名单:"+obj1.Powers+"\n";
msg += "第一轮过后,胜利者为:"+obj1.winner.name +" ,参赛者年龄:"+obj1.winner.age+" ,来自岛国: "+obj1.winner.from+"\n";
msg += "\n\n B组 对战形式:\n\n"
msg += obj1_clone.Team+" 组 ,人员名单:"+obj1_clone.Powers+"\n";
msg += "第一轮过后,胜利者为:"+obj1_clone.winner.name +" ,参赛者年龄:"+obj1_clone.winner.age+" ,来自国际警察部队: "+obj1_clone.winner.from+"\n";
alert(msg);
//-->
</SCRIPT>
</BODY>
</HTML>
其它对像的equals 方法的样例:
后面一个,我重定义了 Boolean 构造函数,并实现了它的toStirng()方法.
可以瞅瞅.
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<META NAME="Generator" CONTENT="Wawa Editor 1.0">
<META NAME="Author" CONTENT="八神奄">
<META NAME="Keywords" CONTENT="Javascript,Java,XML,XSLT,ASP,VBScript,ASP .net,C#,C++,Database">
<META NAME="Description" CONTENT="不及格的程序员,无所不在">
</HEAD>
<BODY>
var a = new Object(); a.arr = new Array("a","b","c");a.name="a"; a.alert = function(){alert()}<br>
var b = new Object(); b.arr = new Array("a","b"); b.name="a"; b.alert = function(){}<br>
var str = new String("abc");<br>
var str_1 = "abc";<br>
var str_2 = "abd";<br>
var c = a;<br>
var d = b;<br>
<SCRIPT LANGUAGE="JavaScript">
<!--
function Object.prototype.equals(obj){
if(this == obj)return true;
if(typeof(obj)=="undefined"||obj==null||typeof(obj)!="object")return false;
var length = 0; var length1=0;
for(var ele in this) length++;for(var ele in obj) length1++;
if(length!=length1) return false;
if(obj.constructor==this.constructor){
for(var ele in this){
if(typeof(this[ele])=="object") {if(!this[ele].equals(obj[ele]))return false;}
else if(typeof(this[ele])=="function"){if(!this[ele].toString().equals(obj[ele].toString())) return false;}
else if(this[ele]!=obj[ele]) return false;
}
return true;
}
return false;
}
function String.prototype.equals(str){
if(this==str)return true;
return false;
}
function Function.prototype.equals(func){
if(this.toString().equals(func.toString()))return true;
return false;
}
function Boolean.prototype.equals(bool){
if(this==bool)return true;
if (bool instanceof Boolean){
return this.toString().equals(bool.toString());
}
return false;
}
var a = new Object();a.arr = new Array("a","b","c");a.name="a"; a.alert = function(){alert()}
var b = new Object(); b.arr = new Array("a","b");b.name="a";b.alert=function(){}
var str = new String("abc");
var str_1 = "abc";
var str_2 = "abc";
var c = a;
var d = b;
alert(" a.equals(b): "+a.equals(b)+"\n\n str.equals(str_1): "+str.equals(str_1)+"\n\n str_1.equals(str_2): "+str_1.equals(str_2)+"\n\n c.equals(a): "+a.equals(c)+"\n\n d.equals(b) : "+b.equals(d)+"\n\n a.alert.equals(b.alert): "+a.alert.equals(b.alert))
</SCRIPT>
<SCRIPT LANGUAGE="JavaScript">
function Boolean(booleans){
if(typeof(booleans)=="undefined"){
this.value = false;
return this;
}else{
if(booleans==null){
this.value = false;
return this;
}
if(booleans==""){
this.value = false;
return this;
}
if(!isNaN(booleans)){
if(booleans<=0){
this.value = false;
}else{
this.value = true;
}
return this;
}
if(booleans!="true"){
this.value = false;
return this;
}else{
this.value = true;
return this;
}
}
}
function Boolean.prototype.toString(){
return this.value ? "true" : "false"
}
document.writeln("两个布尔型对像的比较结果:new Boolean().equeals(new Boolean(\"true\")): "+(new Boolean().equals(new Boolean("true"))));
</SCRIPT>
</BODY>
</HTML>
posted on 2006-03-18 13:28
汪杰 阅读(828)
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