Method for shallow extension of a given object with the properties of passed-in object(s) with support for standards-compliant getters and setters

extend.js

function extend(target) {
  // Run through rest parameters
  Array.prototype.slice.call(arguments, 1).forEach(function (source) {
    if (source) {
      // If source is an array, only copy enumerable properties
      var keys = (Array.isArray(source) ? Object.keys(source) : Object.getOwnPropertyNames(source));

      // Iterate over keys
      keys.forEach(function (key) {
        // Standards-compliant awesomeness
        var descriptor = Object.getOwnPropertyDescriptor(source, key);
        Object.defineProperty(target, key, descriptor);
      });
    }
  });
  return target;
}