function callSomeFunction(someFunction, someArgument){
      return someFunction(someArgument);
    }

    function add10(num){
      return num + 10;
    }
    
    var result1 = callSomeFunction(add10, 10);//調(diào)用add10 把參數(shù)10傳給add10
    alert(result1);  //20
    
    function getGreeting(name){
      return "Hello, " + name;
    }
    
    var result2 = callSomeFunction(getGreeting, "Nicholas");
    alert(result2);  //Hello, Nicholas

function createComparisonFunction(propertyName) {
    
      return function(object1, object2){
        var value1 = object1[propertyName];
        var value2 = object2[propertyName];
    
        if (value1 < value2){
          return -1;
        } else if (value1 > value2){
          return 1;
        } else {
          return 0;
        }
      };
    }

    var data = [{name: "Zachary", age: 28}, {name: "Nicholas", age: 29}];
    
    data.sort(createComparisonFunction("name"));//sort函數(shù)接收一個函數(shù)作為排序的參考，函數(shù)createComparisonFuntion返回了一個匿名的排序函數(shù)
    alert(data[0].name); //Nicholas
    
    data.sort(createComparisonFunction("age"));
    alert(data[0].name); //Zachary    

 function sum(num1, num2){
      return num1 + num2;
    }
    
    function callSum1(num1, num2){
      return sum.apply(this, arguments);//sum函數(shù)請求把callSum1的指針傳給自己，并作計算，此時的this指向callSum1
    }
    
    function callSum2(num1, num2){
      return sum.apply(this, [num1, num2]);
    }
    
    alert(callSum1(10,10));  //20
    alert(callSum2(10,10));  //20

function outer(){
      inner();
    }
    
    function inner(){
      alert(inner.caller);
    }
    
    outer();
caller

//返回一個對函數(shù)的引用，該函數(shù)調(diào)用了當(dāng)前函數(shù)。

function outer(){
      inner();
    }
    function inner(){
      alert(arguments.callee.caller);
      //argments.callee就是函數(shù)體本身，arguments.callee.caller就是函數(shù)體的調(diào)用函數(shù)體
    }
    outer();


function factorial(num){
      if (num <= 1) {
        return 1;
      } else {
        return num * arguments.callee(num-1)//callee當(dāng)前函數(shù)的引用即factorial函數(shù)本身的函數(shù)體
      }
    }

    var trueFactorial = factorial;
    
    factorial = function(){
      return 0;
    };
    
    alert(trueFactorial(5));  //120
    alert(factorial(5));    //0

 window.color = "red";
    var o = { color: "blue" };
              
    function sayColor(){
      alert(this.color);
    }
    var objectSayColor = sayColor.bind(o);
    objectSayColor();  //blue
    /*
      bind主要是為了改變函數(shù)內(nèi)部的this指向，這個是在ECMA5以后加入的，所以IE8一下的瀏覽器不支持
      bind方法會創(chuàng)建一個新函數(shù),稱為綁定函數(shù).當(dāng)調(diào)用這個綁定函數(shù)時,綁定函數(shù)會以創(chuàng)建它時傳入bind方法的第一個參數(shù)作為this,
      傳入bind方法的第二個以及以后的參數(shù)加上綁定函數(shù)運行時本身的參數(shù)按照順序作為原函數(shù)的參數(shù)來調(diào)用原函數(shù).
    */

window.color = "red";
    var o = { color: "blue" };
    
    function sayColor(){
      alert(this.color);
    }
    
    sayColor();      //red
    
    sayColor.call(this);  //red 此時this指向window
    sayColor.call(window); //red 同上
    sayColor.call(o);   //blue 此時sayColor的指針指向o

 function sum(num1, num2){
      return num1 + num2;
    }
    
    function callSum(num1, num2){
      return sum.call(this, num1, num2);
    }
    
    alert(callSum(10,10));  //20

function sayName(name){
      alert(name);
    }   
    
    function sum(num1, num2){
      return num1 + num2;
    }
    
    function sayHi(){
      alert("hi");
    }
    
    alert(sayName.length); //1
    alert(sum.length);   //2
    alert(sayHi.length);  //0
    //實際返回的是函數(shù)的參數(shù)的長度