javascript object problem

i am a little confused. i want to create a javascript object like:

f开发者_如何转开发unction myObject(){
this.keyOne=1;
this.keyTwo=2;
this.keyThree=3;

function add(){
return this.keyOne+this.keyTwo+this.keyThree;
}

return{
    add: add
}

}

so creating this object with

var newObject = new myObject();

is working fine and all attributes are correct. but with

var result = newObject.add;

all keys are suddenly undefined! i have no idea why? :/

You're not defining add() in a way that's exposed, you could do this for example:

function myObject(){
    this.keyOne=1;
    this.keyTwo=2;
    this.keyThree=3;

    this.add = function(){
      return this.keyOne+this.keyTwo+this.keyThree;
    }
}
var newObject = new myObject();
var result = newObject.add();

You can test it here.

Also note that you need to call add() with parenthesis, since it's a function, or you'll get the function itself back, not the result.

There currently is no meaning for the keyword public in standard JavaScript.

Based on your original code snippet, I suspect you meant:

function myObject(){
    this.keyOne=1;
    this.keyTwo=2;
    this.keyThree=3;

    function add(){
        return this.keyOne+this.keyTwo+this.keyThree;
    }

    return {
        add: add
    };
}

The function would then return an object that only has one property: the add function. That object is created by the object literal after the return keyword.

But then there is no point using this. You could have written:

function myObject() {

    var keyOne=1;
    var keyTwo=2;
    var keyThree=3;

    function add() {
        return keyOne + keyTwo + keyThree;
    }

    return {
        add: add
    };
}

Or even more succinctly:

function myObject() {

    var keyOne=1;
    var keyTwo=2;
    var keyThree=3;

    return {
        add: function() {
            return keyOne + keyTwo + keyThree;
        }
    };
}

This has the added advantage that you don't need to call it prefixed with new. It's just an ordinary function that creates and returns an object which contains another function:

var o = myObject();
alert(o.add());

You could allow the caller to specify the numbers to be added, like this:

function myObject(keyOne, keyTwo, keyThree) {

    return {
        add: function() {
            return keyOne + keyTwo + keyThree;
        }
    };
}

var o = myObject(5, 4, 7);
alert(o.add());