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Notes on arguments in js

高洛峰

Dec 14, 2016 am 09:13 AM

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
<title>water_down_前端开发 </title>
<style type="text/css">
body{margin:0;padding:0}
</style>
</head>
<body>
water Dwon!
</body>
<script type="text/javascript">
var waterDown = function(funa, funb){
    /*
     * arguments 对象只有函数开始才会创建
     * 先看一下arguments的类型 ie和opera下均为[object Object]，
     * 但是ff、chrome、safari下直接为[object Arguments], 说明这个arguments有特殊性
     */
    alert(Object.prototype.toString.apply(arguments));
    
    /*
     * 看一下它的实例 function Object() {  [native code] }
     * 是一个Object类型的实例 
     * arguments = {
     *     0 : "water",
     *     1 : "down",
     *     2 : "w",
     *     3 : "d"
     *    }
     * 当然这样的0，1，2...n 这样的属性是不能用 arguments.n  来调用的 
     * 但是可以用访问数组元素的方式来用，arguments[n]
     * 然后又添加了一些属性和方法，感觉似数组吧
     * length属性  参数的个数
     */
    alert(arguments.constructor)
    //alert(["a","b"].constructor) 

    /*
     * callee 返回正被执行的 Function 对象
     * 递归就不用说了，都知道
     */
    console.log(arguments.length) //控制台上输出实际传入的参数个数
    console.log(arguments.callee.length) //形参的个数 就是funa，funb

    /*
     * caller 返回一个对函数的引用，就是调用当前函数的函数。
     * 如果函数是由顶层调用的，那么 caller包含的就是 null  
     */
    if(arguments.callee.caller){
        //alert(waterDown.caller.toString())
        alert(arguments.callee.caller.toString())
    }else{
        alert("No wrap Function!")
    }
    
    /*
     * 把arguments 转换成真正的数组
     */
    var A = Array.prototype.slice.call(arguments);
    alert(Object.prototype.toString.apply(A));
}

waterDown("water", "down", "w", "d");

!function(){
    /*
     * 调用waterDown函数 此时waterDown.caller就是当前匿名函数
     * 而waterDown.caller.toString() 就等于把当前匿名函数反编译喽
     */
    waterDown("waterDown");
}()
</script>
</html>

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