An implementation of the extend function for object mixin

extend.js

// Taken from
// http://raganwald.com/2014/04/10/mixins-forwarding-delegation.html

(function(window) {
  var __slice = [].slice;

  function extend () {
    var consumer = arguments[0],
        providers = __slice.call(arguments, 1),
        key,
        i,
        provider,
        except;
  
    for (i = 0; i < providers.length; ++i) {
      provider = providers[i];
      except = provider['except'] || [];
      except.push('except');
      for (key in provider) {
        if (except.indexOf(key) < 0 && provider.hasOwnProperty(key)) {
          consumer[key] = provider[key];
        };
      };
    };
    return consumer;
  };
  
  window.extend = extend;
})(window);