Extending Javascript objects with CoffeeScript

coffeescript

Solution

You can try adding an explicit `return`:

Object::extend = (objects...) ->
    for object in objects
        for key, value of object
            @[key] = value
    return

That produces this:

var __slice = [].slice;

Object.prototype.extend = function() {
  var key, object, objects, value, _i, _len;
  objects = 1 <= arguments.length ? __slice.call(arguments, 0) : [];
  for (_i = 0, _len = objects.length; _i < _len; _i++) {
    object = objects[_i];
    for (key in object) {
      value = object[key];
      this[key] = value;
    }
  }
};

Every CoffeeScript function returns the value of the last expression in the function, CoffeeScript loops are also expressions. That means that CoffeeScript has to build all that `_results` stuff to produce a return value for your function since you had an implicit `return` applying to the outer loop. If you remove that implicit `return` by adding an explicit "return nothing" then the CS→JS compiler seems to be smart enough to not do all that extra `_results` work.

Problem

I want to add the ability to extend javascript objects by adding a method to the prototype. The method will receive one or more other objects and will add all of the key/values to `this`. This is what I came up with: ``` Object::extend = (objects...) -> @[key] = value for key, value of object for object in objects ``` or this: ``` Object::extend = (objects...) -> for object in objects for key, value of object @[key] = value ``` Both work as expected, and compile into the same javascript code: ``` var __slice = [].slice; Object.prototype.extend = function() { var key, object, objects, value, _i, _len, _results; objects = 1 <= arguments.length ? __slice.call(arguments, 0) : []; _results = []; for (_i = 0, _len = objects.length; _i < _len; _i++) { object = objects[_i]; _results.push((function() { var _results1; _results1 = []; for (key in object) { value = object[key]; _results1.push(this[key] = value); } return _results1; }).call(this)); } return _results; }; ``` What I'm not too happy about is the whole results thing that is created per for loop which is completely redundant for my purpose. Is there a way to get a code more like: ``` Object.prototype.extend = function() { var key, object, objects, value, _i, _len; objects = 1 <= arguments.length ? __slice.call(arguments, 0) : []; for (_i = 0, _len = objects.length; _i < _len; _i++) { object = objects[_i]; (function() { for (key in object) { value = object[key]; this[key] = value; } }).call(this); } }; ``` Thanks. Edit I'm aware that I can simply embed javascript code, but looking for a coffeescript solution.

Original source