map function for objects (instead of arrays)

Question

I have an object:

myObject = { \'a\': 1, \'b\': 2, \'c\': 3 }

I am looking for a native method, similar to Array.prototype.map

Answer 1

It's pretty easy to write one:

Object.map = function(o, f, ctx) {
    ctx = ctx || this;
    var result = {};
    Object.keys(o).forEach(function(k) {
        result[k] = f.call(ctx, o[k], k, o); 
    });
    return result;
}

with example code:

> o = { a: 1, b: 2, c: 3 };
> r = Object.map(o, function(v, k, o) {
     return v * v;
  });
> r
{ a : 1, b: 4, c: 9 }

NB: this version also allows you to (optionally) set the this context for the callback, just like the Array method.

EDIT - changed to remove use of Object.prototype, to ensure that it doesn't clash with any existing property named map on the object.