var write = document.write;  
write("hello");  
//1.以上代码有什么问题 
//2.正确操作是怎样的 

var write = document.write; 
write.bind(document)('hello'); 

var write = document.write; 
write.call(document,'hello'); 

var write = document.write; 
write.apply(document,['hello']); 

<script type="text/javascript"> 
 
this.num = 9;  
var module = {  
  num: 81, 
  getNum: function(){ 
    console.log(this.num); 
  } 
}; 
 
module.getNum(); // 81 ,this->module 
 
var getNum = module.getNum; 
getNum(); // 9, this->window or global 
 
var boundGetNum = getNum.bind(module);  
boundGetNum(); // 81,this->module 
 
</script> 

<script type="text/javascript"> 
 
function list() {  
 return Array.prototype.slice.call(arguments); 
} 
 
var list1 = list(1, 2, 3); 
console.log(list1);// [1, 2, 3] 
 
// 预定义参数37 
var leadingThirtysevenList = list.bind(undefined, 37); 
 
var list2 = leadingThirtysevenList(); 
console.log(list2);// [37]  
 
var list3 = leadingThirtysevenList(1, 2, 3); 
console.log(list3);// [37, 1, 2, 3]  
</script>

<script type="text/javascript"> 
 
function Bloomer() {  
 this.petalCount = Math.ceil(Math.random() * 12) + 1; 
} 
 
// 1秒后调用declare函数 
Bloomer.prototype.bloom = function() {  
 window.setTimeout(this.declare.bind(this), 1000); 
}; 
 
Bloomer.prototype.declare = function() {  
 console.log('我有 ' + this.petalCount + ' 朵花瓣!'); 
}; 
 
var test = new Bloomer(); 
 
test.bloom(); 
 
</script> 

<script type="text/javascript"> 
 
function Point(x, y) {  
 
 this.x = x; 
 this.y = y; 
} 
 
Point.prototype.toString = function() {  
 console.log(this.x + ',' + this.y); 
}; 
 
var p = new Point(1, 2);  
p.toString(); // 1,2 
 
var YAxisPoint = Point.bind(null,10); 
var axisPoint = new YAxisPoint(5);  
axisPoint.toString(); // 10,5 
 
console.log(axisPoint instanceof Point); // true  
console.log(axisPoint instanceof YAxisPoint); // true  
console.log(new Point(17, 42) instanceof YAxisPoint); // true  
</script>

Function.prototype.bind = function(context){  
 self = this; //保存this，即调用bind方法的目标函数 
 return function(){ 
   return self.apply(context,arguments); 
 }; 
}; 

Function.prototype.bind = function(context){  
 var args = Array.prototype.slice.call(arguments, 1), 
 self = this; 
 return function(){ 
   var innerArgs = Array.prototype.slice.call(arguments); 
   var finalArgs = args.concat(innerArgs); 
   return self.apply(context,finalArgs); 
 };<BR>｝ 

Function.prototype.bind = function(context){  
 var args = Array.prototype.slice(arguments, 1), 
 F = function(){}, 
 self = this, 
 bound = function(){ 
   var innerArgs = Array.prototype.slice.call(arguments); 
   var finalArgs = args.concat(innerArgs); 
   return self.apply((this instanceof F ? this : context), finalArgs); 
 }; 
 
 F.prototype = self.prototype; 
 bound.prototype = new F(); 
 return bound; 
}; 

Function.prototype.bind = function (oThis) {  
  if (typeof this !== "function") { 
   throw new TypeError("Function.prototype.bind - what is trying to be bound is not callable"); 
  } 
 
  var aArgs = Array.prototype.slice.call(arguments, 1), 
    fToBind = this, 
    fNOP = function () {}, 
    fBound = function () { 
     return fToBind.apply( 
       this instanceof fNOP && oThis ? this : oThis || window, 
       aArgs.concat(Array.prototype.slice.call(arguments)) 
     ); 
    }; 
 
  fNOP.prototype = this.prototype; 
  fBound.prototype = new fNOP(); 
 
  return fBound; 
};