Function calling a function within an object

Question

Suppose I have a Javascript object (the curly braces indicate it is so):

{
 a: function (something) {
 return something*2;
 },
 b: function () {
 var c = this.a(2); //Does not work. Why?
 return c;
 }
}

What is the workaround to this?

• John Dvorak: This should work. How are you calling b?
• Evan Davis: The value of this is entirely dependent on how you are calling b() and cannot be answered otherwise.
• bibo bode: Mathletics is correct. I was calling a from another function within b, which affects "this". The trick is to save "this" before entering that function within b.
• Evan Davis: Voted to close as not a real question.
• bibo bode: Mathletics, I asked this question after searching around SO for an hour. I'm sure it will help someone else out.

Answer 1

It not work because when you access the method b it context isn't the instance from object that you made, it will try to search in the binded context or in window object.

var x = {
 a: function (something) {
 return something*2;
 },
 b: function () {
 var c = x.a(2); //Does not work. Why?
 return c;
 }
}

This way you are using the x as context to access the method a.

Or you can use a new operator to create your object and the method as it prototype or direct method.

When you do it, the result will be:

var x = function() {
 return {
 a: function (something) {
 return something*2;
 },
 b: function () {
 var c = this.a(2); //Does not work. Why?
 return c;
 }
 }
}

It will make you lose the prototype from x, when you make a new instance, but your code will work.

Example:

var y = new x();
console.log(y.b());

• bfavaretto: I thought x = was implied on the question. If not, how could the OP possibly be calling b?
• Gabriel Gartz: yes, x is inside b method context. I did just put there for an example of use. This way you cant make it won't work using x.b.apply(window); for example.

Answer 2

It works for me, you were missing a coma after a declaration.

{
 a: function (something) {
 return something*2;
 }, // -> this one
 b: function () {
 var c = this.a(2);
 return c;
 }
}

If you call b the function should return a(2) which is 2*2=4

alert(p.b());

http://jsfiddle.net/PNbXj/

• jholloman: Just a syntax error :) (I typed it manually and was wondering what was wrong, good find)