面向对象（this的问题二）
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
<script>
function zgz()
{
var _this=this
this.a=5;
document.getElementById('btn').onclick=function(){
_this.show();
}
}
zgz.prototype.show=function(){
alert(this.a)
}
window.onload=function(){
new zgz();
}
</script>
</head>
<body>
<input id="btn" type="button" value="按钮">
</body>
</html>
