40行实现javascript继承

最新推荐文章于 2025-03-20 22:14:41 发布

翻译最新推荐文章于 2025-03-20 22:14:41 发布 · 403 阅读

本文介绍了一种使用JavaScript实现的继承模式，通过构造函数和原型链来创建可扩展的类。该模式支持方法覆盖，并能保留对超类方法的调用。

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来自john resig

( function (argument) {
	var initialzing = false;
	var fnTest = /\b_super\b/;
	//this is window, and this statement let live Class in window
	this.Class = function (){};
	//create a new class that inherits this class
	Class.extend = function ( prop ) {
		var _super = this.prototype;
		initialzing = true;
		var prototype = new this();
		initialzing = false;
		for ( var name in prop ) {
			var haveSuper = typeof prop[ name ] == "function" && typeof _super[ name ] == "function" && fnTest.test( prop[ name ] )
			if ( haveSuper ) {
				prototype[ name ] = ( function ( name , fn ) {
					return function () {
						var tmp = this._super;
						this._super = _super[ name ];
						var ret = fn.apply( this , arguments );
						this._super = tmp;
						return ret;
					};
				} ) ( name , prop[ name ] );
			} else {
				prototype[ name ] = prop[ name ];
			}
		}
		function Class () {
			if ( !initialzing && this.init )
				this.init.apply( this , arguments );
		}
		Class.prototype = prototype;
		Class.prototype.constructor = Class;
		Class.extend = arguments.callee;
		return  Class;
	};
} )();

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(){
    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