JS – 实现面向对象
公有和私有
function Person() { var name = "abc"; // private var age = 100; // private this.show = function() { // 公有方法, 要访问私有变量只能这么做 window.alert(‘name = ‘ + name); }; function f() { alert(‘这是一个私有方法‘); } } p.new_func = function() { document.write(‘I want to access to private FAIL‘); alert(p.name); // undefined }; p.new_func();
继承
通过原型实现继承
function tiger() { } function cat() { this.climb = function () { alert(‘cat cat‘); } } tiger.prototype = new cat(); var t1 = new tiger(); var c1 = new cat(); t1.climb();
对象冒充
function Animal(name, age) { this.name = name; this.age = age; } function Dog(name, age) { this.animal = Animal; this.animal(name, age); } var dog = new Dog(‘a dog‘, 2); document.write(Dog.name); if (Dog instanceof Animal) { alert(‘Dog 是 Animal 的实例‘); // 是 }
对象复制
function cat() { this.climb = function () { alert(‘cat cat‘); } } function tiger() { this.extend = function (parent) { for (var key in parent) { this[key] = parent[key]; } } } var t1 = new tiger(); t1.extend(new cat()); t1.climb();
通过 call/apply 实现 对象继承
function Stu(name, age) { this.name = name; this.age = age; this.show = function () { alert(this.name + ‘ age is ‘ + this.age); } } function MidStu(name, age) { Stu.call(this, name, age); } var m = new MidStu(‘one‘, 23); m.show();
function cat() { this.climb = function () { alert(‘cat cat‘); } } function tiger() { this.parent = cat; this.parent.apply(this, arguments); delete this.parent; } var t1 = new tiger(); var c1 = new cat(); t1.climb();
function Dog() { Dog.prototype.shout = function () { document.write("wang wang wang"); }; } var dog = new Dog(); dog.shout(); // 给 array 增加一个 find 方法 Array.prototype.find = function(val) { var len = this.length; for (var i = 0; i < len; i++) { if (val == this[i]) { return i; } } };
原形
原型的好处: 不会重复创建新的方法, 新的属性, 节省内存
function Dog(name) { this.name = name; this.func = function () { alert(‘....‘); }; } var dog1 = new Dog(‘aa‘); var dog2 = new Dog(‘bb‘); if (dog1.func == dog2.func) { // 输出不相等 alert(‘相等‘); } else { alert(‘不相等‘); } Dog.prototype.func2 = function() { alert(‘new fun‘); }; var dog3 = new Dog(‘aa‘); var dog4 = new Dog(‘bb‘); if (dog3.func2 == dog4.func2) { // 输出相等 alert(‘相等‘); } else { alert(‘不相等‘); }
TODO 工厂方法
// 如果对象只有一个的时候可以这样用, 不被继承... (工厂方法) var p = new Object(); p.name = .... p.age = ...
