javascript访问新创建的对象

Question

If

function foos(){alert(this)}
x=new foos() which is==={foo();}//as this keyword points to Object object

so than i can say foos as the method of that new object but when i do this

x.foos();//after the object is initialized,it dont work at all why?

Answer 1

The code creates an instance of foos on which foos is not defined as a property on that object.

If you want to add a property on an object try something like:

function foos(){
  this.myProp = "Hello";
}

var x = new foos();

alert(x.myProp);

If you want to add a method to an object use:

foos.prototype.myFunc = function(){
  alert(this.myProp);
};

x.myFunc(); //alerts Hello

Answer 2

'foos' is the constructor function and it will not be part of the newly object methods, if u want to add methods u can use it like this:

function MyClass() { }

MyClass.prototype.foos = function () {
    alert(this);
}

and then:

var x = new MyClass();
x.foos();