生成器和迭代器(仅适用于Firefox 2+和Safari)。

function fib() {
  var i = 0, j = 1;
  while (true) {
    yield i;
    var t = i;
    i = j;
    j += t;
  }
}

var g = fib();
for (var i = 0; i < 10; i++) {
  document.write(g.next() + "<br>\n");
}

The function containing the yield keyword is a generator. When you call it, its formal parameters are bound to actual arguments, but its body isn't actually evaluated. Instead, a generator-iterator is returned. Each call to the generator-iterator's next() method performs another pass through the iterative algorithm. Each step's value is the value specified by the yield keyword. Think of yield as the generator-iterator version of return, indicating the boundary between each iteration of the algorithm. Each time you call next(), the generator code resumes from the statement following the yield. In normal usage, iterator objects are "invisible"; you won't need to operate on them explicitly, but will instead use JavaScript's for...in and for each...in statements to loop naturally over the keys and/or values of objects.

var objectWithIterator = getObjectSomehow();

for (var i in objectWithIterator)
{
  document.write(objectWithIterator[i] + "<br>\n");
}

也许对某些人来说有点明显…

安装Firebug并使用console.log("hello")。这比使用随机alert();好多了，我记得几年前我经常这样做。

当你想从数组中删除一个元素时，可以使用delete操作符，如下所示:

var numbers = [1,2,3,4,5];
delete numbers[3];
//numbers is now [1,2,3,undefined,5]

正如您所看到的，元素被删除了，但是数组中留下了一个洞，因为元素被替换为一个未定义的值。

因此，要解决这个问题，不要使用删除，而是使用splice array方法…是这样的:

var numbers = [1,2,3,4,5];
numbers.splice(3,1);
//numbers is now [1,2,3,5]

splice的第一个参数是数组[index]中的序数，第二个参数是要删除的元素数量。

当你写回调时，你有很多代码，看起来像这样:

callback: function(){
  stuff(arg1,arg2);
}

您可以使用下面的函数使它更简洁。

callback: _(stuff, arg1, arg2) 

它使用javascript的function对象中一个不太为人所知的函数apply。

它还显示了另一个可以用作函数名的字符:_。

function _(){
        var func;
        var args = new Array();
        for(var i = 0; i < arguments.length; i++){
                if( i == 0){
                        func = arguments[i];
                } else {
                        args.push(arguments[i]);
                }
        }
        return function(){
                return func.apply(func, args);
        }
}

您还可以使用前面提到的原型链spoon16扩展(继承)类和重写属性/方法。

在下面的例子中，我们创建了一个类Pet并定义了一些属性。我们还重写了继承自Object的. tostring()方法。

在此之后，我们创建了一个Dog类，它扩展了Pet并重写了. tostring()方法，再次改变了它的行为(多态性)。此外，我们还向子类添加了一些其他属性。

在此之后，我们检查继承链以显示Dog仍然是Dog类型、Pet类型和Object类型。

// Defines a Pet class constructor 
function Pet(name) 
{
    this.getName = function() { return name; };
    this.setName = function(newName) { name = newName; };
}

// Adds the Pet.toString() function for all Pet objects
Pet.prototype.toString = function() 
{
    return 'This pets name is: ' + this.getName();
};
// end of class Pet

// Define Dog class constructor (Dog : Pet) 
function Dog(name, breed) 
{
    // think Dog : base(name) 
    Pet.call(this, name);
    this.getBreed = function() { return breed; };
}

// this makes Dog.prototype inherit from Pet.prototype
Dog.prototype = new Pet();

// Currently Pet.prototype.constructor
// points to Pet. We want our Dog instances'
// constructor to point to Dog.
Dog.prototype.constructor = Dog;

// Now we override Pet.prototype.toString
Dog.prototype.toString = function() 
{
    return 'This dogs name is: ' + this.getName() + 
        ', and its breed is: ' + this.getBreed();
};
// end of class Dog

var parrotty = new Pet('Parrotty the Parrot');
var dog = new Dog('Buddy', 'Great Dane');
// test the new toString()
alert(parrotty);
alert(dog);

// Testing instanceof (similar to the `is` operator)
alert('Is dog instance of Dog? ' + (dog instanceof Dog)); //true
alert('Is dog instance of Pet? ' + (dog instanceof Pet)); //true
alert('Is dog instance of Object? ' + (dog instanceof Object)); //true

这个问题的两个答案都是从Ray Djajadinata的一篇很棒的MSDN文章中修改的代码。

使用函数。Apply用于指定函数将作用的对象:

假设你有一个类

function myClass(){
 this.fun = function(){
   do something;
 };
}

如果之后你这样做了:

var a = new myClass();
var b = new myClass();

myClass.fun.apply(b); //this will be like b.fun();

您甚至可以指定一个调用参数数组作为第二个参数

看这个:https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/Function/apply