prototype 属性使您有能力向对象添加属性和方法。
<!DOCTYPE html>
<html lang="zh-cn">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<script type="text/javascript">
//向 自定义对象 添加属性或方法
function employee(name,job,born){
this.name=name;
this.job=job;
this.born=born;
}
var bill=new employee("Bill Gates","Engineer",1985);
employee.prototype.salary=null;
bill.salary=20000;
document.write(bill.salary);
</script>
</body>
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