求助javascript,创建一个类classA，使得 new classA === new classA()该怎么写啊？

Question

求助javascript,创建一个类classA，使得 new classA === new classA()该怎么写啊？

在此谢过各位了！

Answer 1

单例模式？？？？

var ClassA = function(){

    if(ClassA.instance == null)
    {
        ClassA.instance = this;
    }
    return ClassA.instance;
}

console.log(new ClassA === new ClassA());
// 这里输出true

Answer 2

如 @freewolf 所说，单例是一种方式。

当然，如果你只是想hack玩玩，那还有其他方式：

var A = function() {
    return A;
};

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

console.log(a === b);//true

奇怪吧？， 看new操作符的说明：

When the code new Foo(...) is executed, the following things happen:

1. A new object is created, inheriting from Foo.prototype.

2. The constructor function Foo is called with the specified arguments and this bound to the newly created object. new Foo is equivalent to new Foo(), i.e. if no argument list is specified, Foo is called without arguments.

3. The object returned by the constructor function becomes the result of the whole new expression. If the constructor function doesn't explicitly return an object, the object created in step 1 is used instead. (Normally constructors don't return a value, but they can choose to do so if they want to override the normal object creation process.)