JS中prototype關(guān)鍵字的功能介紹及使用示例

2019-11-20 22:30:14

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供稿：網(wǎng)友

prototype 關(guān)鍵字可以為 JS原有對(duì)象或者自己創(chuàng)建的類中添加方法或者屬性。
也可以實(shí)現(xiàn)繼承。
例子：

 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>JS中 prototype 關(guān)鍵字的使用</title> 
</head> 
<script> 
<!-- demo1 JS中原有對(duì)象中 添加方法 --> 
Number.prototype.add = function (num){ 
return this+num; 
} 
function but1_click(){ 
alert((3).add(8)); 
} 
<!-- demo2 JS中新建對(duì)象中， 添加屬性 ，方法 --> 
function Car(cColor,cWeight){ 
this.cColor = cColor; 
this.cWeight = cWeight; 
} 
Car.prototype.drivers = new Array('zhangsan','lisi'); 
Car.prototype.work = function (cLong){ 
alert("我跑了"+cLong+"公里"); 
} 
function but2_click(){ 
var c = new Car("red","5"); 
c.drivers.push('zhaoliu'); 
alert(c.drivers); 
c.work(1); 
} 
<!-- demo3 JS中新建對(duì)象中， 添加屬性 ，方法 緊湊的寫法 --> 
function Rectangle(rWeight,rHeight){ 
this.rWeight = rWeight; 
this.rHeight = rHeight; 
if( typeof this._init == 'undefined'){ 
Rectangle.prototype.test = function (){ 
alert("test"); 
} 
} 
this._init = true; 
} 
function but3_click(){ 
var t = new Rectangle(6,8); 
t.test(); 
} 
<!-- demo4 prototype 繼承 --> 
function objectA(){ 
this.methodA = function (){ 
alert("我是A方法"); 
} 
} 
function objectB(){ 
this.methodB = function (){ 
alert("我是B方法"); 
} 
} 
objectB.prototype = new objectA(); 
function but4_click(){ 
var t = new objectB(); 
t.methodB(); 
t.methodA(); 
} 
</script> 
<body> 
<h2> prototype 關(guān)鍵字的使用 </h2> 
<hr /> 
<input id="but1" type="button" value="demo1" onclick="but1_click()" /> 
<input id="but2" type="button" value="demo2" onclick="but2_click()" /> 
<input id="but3" type="button" value="demo3" onclick="but3_click()" /> 
<input id="but4" type="button" value="demo4" onclick="but4_click()" /> 
</body> 
</html> 