本文实例讲述了JavaScript中的类与实例实现方法。分享给大家供大家参考。具体如下:
JavaScript 中没有父类, 子类的概念, 也没有class 和 instance 的概念, 全靠 prototype chain来实现继承. 当查找一个对象的属性时, JavaScript 会向上遍历 prototype chain, 直到找到对应的属性为止. 有几种方法, 可以使得 JavaScript 模拟出 class 和 instance 的概念.
1. 直接使用构造函数来创建对象, 在构造函数内部使用 this指代对象实例.
function Animal() { this.name = "animal"; } Animal.prototype.makeSound = function() { console.log("animal sound"); } [Function] var animal1 = new Animal(); animal1.name; 'animal' animal1.makeSound(); animal sound
function Point(x, y) { this.x = x; this.y = y; } Point.prototype = { method1: function() { console.log("method1"); }, method2: function() { console.log("method2"); }, } { method1: [Function], method2: [Function] } var point1 = new Point(10, 20); point1.method1(); method1 point1.method2(); method2
2. 使用 Object.create()方法来创建对象
var Animal = { name: "animal", makeSound: function() { console.log("animal sound"); }, } var animal2 = Object.create(Animal); animal2.name; 'animal' console.log(animal2.name); animal animal2.makeSound(); animal sound
3. 荷兰程序员 Gabor de Mooij 提出的极简主义法(minimalist approach). 推荐用法.
var Animal = { init: function() { var animal = {}; animal.name = "animal"; animal.makeSound = function() { console.log("animal sound"); }; return animal; } }; var animal3 = Animal.init(); animal3.name; 'animal' animal3.makeSound(); animal sound
var Cat = { init: function() { var cat = Animal.init(); cat.name2 = "cat"; cat.makeSound = function() { console.log("cat sound"); }; cat.sleep = function() { console.log("cat sleep"); }; return cat; } } var cat = Cat.init(); cat.name; // 'animal' cat.name2; // 'cat' cat.makeSound(); // 类似于方法的重载 cat sound cat.sleep(); cat sleep
var Animal = { init: function() { var animal = {}; var sound = "private animal sound"; // 私有属性 animal.makeSound = function() { console.log(sound); }; return animal; } }; var animal4 = Animal.init(); Animal.sound; // undefined 私有属性只能通过对象自身的方法来读取. animal.sound; // undefined 私有属性只能通过对象自身的方法来读取 animal4.makeSound(); private animal sound
var Animal = { sound: "common animal sound", init: function() { var animal = {}; animal.commonSound = function() { console.log(Animal.sound); }; animal.changeSound = function() { Animal.sound = "common animal sound changed"; }; return animal; } } var animal5 = Animal.init(); var animal6 = Animal.init(); Animal.sound; // 可以视为类属性 'common animal sound' animal5.sound; // 实例对象不能访问类属性 undefined animal6.sound; undefined animal5.commonSound(); common animal sound animal6.commonSound(); common animal sound animal5.changeSound(); // 修改类属性 undefined Animal.sound; 'common animal sound' animal5.commonSound(); common animal sound animal6.commonSound(); common animal sound
希望本文所述对大家的javascript程序设计有所帮助。