A simplified and intuitive way to define objects properties

Object.prototype.define.js

(function (Object) {
  
  /**
   * @name         Object.prototype.define
   * @description  A simplified and intuitive way to define objects properties.
   * @requires     Object.defineProperty, Array.prototype.forEach (native or shimmed)
   * @author       Andrea Giammarchi (@WebReflection)
   * @license      Mit Style
   */
  
  // function reused for every defined property
  function assign(key, i, descriptor) {
    
    // if descriptor is not present
    // last valid one is recycled
    // handy to define multiple properties
    // with the same type
    if (i in this.d) {
      last = i;
    }
    descriptor = this.d[last];
    
    // if descriptor is not an object
    if (typeof descriptor != "object" || descriptor == null) {
      // the descriptor is created runtime
      descriptor = {
        value: descriptor
      };
    }
    
    // by default defined properties should not be redefined
    // otherwise there could be unexpected results
    if (!hasOwnProperty.call(descriptor, "configurable")) {
      descriptor.configurable = false;
    }
    
    // by default properties are writeable
    // unless the property is not a method
    // so that methods cannot be changed runtime
    if (
      !hasOwnProperty.call(descriptor, "writable") &&
      !(
        hasOwnProperty.call(descriptor, "set") ||
        hasOwnProperty.call(descriptor, "get")
      )
    ) {
      descriptor.writable = typeof descriptor.value != "function";
    }
    
    // by convention all property names that starts with underscore
    // are considered not enumerable
    if (!hasOwnProperty.call(descriptor, "enumerable")) {
      descriptor.enumerable = key.charAt(0) != "_";
    }
    
    // we can define now the property after all handy checks
    defineProperty(this.r, key, descriptor);
  }
  
  var // private shortcuts shared across this scope
    defineProperty = Object.defineProperty,
    hasOwnProperty = {}.hasOwnProperty,
    a = [],
    concat = a.concat,
    last = 0,
    define = "define"
  ;
  
  // if not defined already ...
  define in Object.prototype || defineProperty(
    // set the method and do not let others change it
    Object.prototype,
    define,
    {
      enumerable: false,
      configurable: false,
      writable: false,
      value: function defining(
        keys,       // String or Array of Strings
        descriptors // Object or Array of Objects
      ) {
        concat.call(a, keys).forEach(
          assign,
          {
            // reference
            r: this,
            // descriptors
            d: concat.call(a, descriptors)
          }
        );
        last = 0;
        return this;
      }
    }
  );
  
}(Object));