 
//階乘 
function factorial(num) { 
if (num <= 1) { 
return 1; 
} else { 
return num*arguments.callee(num-1); //用agreements.callee代替 
} 
} 

var trueFactorial = factorial; 
factorial = function { 
return 0; 
} 
alert(trueFactorial(5)); //20 
alert(factorial(5)); //0 

2.函數(shù)的屬性和方法
length屬性，表示函數(shù)參數(shù)的個(gè)數(shù)

3. apply()和call()方法
apply()和call()方法的作用是傳遞參數(shù)或擴(kuò)充函數(shù)的作用域

復(fù)制代碼代碼如下:

 
//傳遞參數(shù) 
function sum(num1,num2) { 
return num1+num2; 
} 
function callSum(num1,num2) { 
return sum.call(this,num1,num2); //第一個(gè)參數(shù)this,后面列舉所有參數(shù) 
} 
alert(callSum(10,10)); //20 

function calSum1(num1,num2) { 
return sum.apply(this,arguments); //第一個(gè)參數(shù)this,第二個(gè)參數(shù)arguments 
} 
function calSum2(num1,num2) { 
return sum.apply(this,[num1,num2]); //第一個(gè)參數(shù)this,第二個(gè)參數(shù)是參數(shù)數(shù)組 
} 
alert(callSum1(10,10)); //20 
alert(callSum2(10,10)); //20 

復(fù)制代碼代碼如下:

 
//改變函數(shù)作用域 
window.color = "red"; 
var o = { color:"blue"}; 
function sayColor() { 
alert(this.color); 
} 
sayColor(); //red 
sayColor.call(this); //red 
sayColor.call(window);//red 
sayColor.call(o); //blue 

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