关于JohnResig继承的实例讲解

最近我们课程到了面向对象这一章节，为了让大家更好的理解面向对象：

var person = class.extend({
  init: function(isdancing){
    this.dancing = isdancing;
  },
  dance: function(){
    return this.dancing;
  }
});
 
var ninja = person.extend({
  init: function(){
    this._super( false );
  },
  dance: function(){
    // call the inherited version of dance()
    return this._super();
  },
  swingsword: function(){
    return true;
  }
});
 
var p = new person(true);
p.dance(); // => true
 
var n = new ninja();
n.dance(); // => false
n.swingsword(); // => true
 
// should all be true
p instanceof person && p instanceof class &&
n instanceof ninja && n instanceof person && n instanceof class

我认为上面的这种api设计是比较nice的，它达到了几个目的：一、所有的类继承自一个祖先class二、子类可以覆盖掉父类上的方法，当然了，可以通过super方法来调用父为的同名方法

下面是我的实现：

/* simple javascript inheritance
 * by john resig https://ejohn.org/
 * mit licensed.
 */
// inspired by base2 and prototype
(function(){
  var initializing = false, fntest = /xyz/.test(function(){xyz;}) ? /\b_super\b/ : /.*/;
 
  // the base class implementation (does nothing)
  this.class = function(){};
 
  // create a new class that inherits from this class
  class.extend = function(prop) {
    var _super = this.prototype;
   
    // instantiate a base class (but only create the instance,
    // don't run the init constructor)
    initializing = true;
    var prototype = new this();
    initializing = false;
   
    // copy the properties over onto the new prototype
    for (var name in prop) {
      // check if we're overwriting an existing function
      prototype[name] = typeof prop[name] == "function" &&
        typeof _super[name] == "function" && fntest.test(prop[name]) ?
        (function(name, fn){
          return function() {
            var tmp = this._super;
           
            // add a new ._super() method that is the same method
            // but on the super-class
            this._super = _super[name];
           
            // the method only need to be bound temporarily, so we
            // remove it when we're done executing
            var ret = fn.apply(this, arguments);        
            this._super = tmp;
           
            return ret;
          };
        })(name, prop[name]) :
        prop[name];
    }
   
    // the dummy class constructor
    function class() {
      // all construction is actually done in the init method
      if ( !initializing && this.init )
        this.init.apply(this, arguments);
    }
   
    // populate our constructed prototype object
    class.prototype = prototype;
   
    // enforce the constructor to be what we expect
    class.prototype.constructor = class;
 
    // and make this class extendable
    class.extend = arguments.callee;
   
    return class;
  };
})();