JavaScript Object只是一个关联数组吗？ [英] Is JavaScript Object nothing but an associative array?

问题描述

好的，我正在浏览JavaScript的基础知识，我正在学习对象我遇到过这个例子......

Ok am just going through basics of JavaScript and I was learning objects where I came across this example...

JavaScript

JavaScript

var person = {
   firstname : "Smith",
   lastname  : "Bach"
};

我们用PHP写的是

$person = array(
    "firstname"=>"Smith", 
    "lastname"=>"Bach"
);

这是同样的事情，或者在理解这个概念时犯了错误？

So is this the same thing or am making a mistake in understanding the concept?

推荐答案

不，对象不止于此。

对象确实是地图/字典，但另外每个对象都从另一个对象继承了一些属性（键值对）。另一个对象称为原型。

Object is indeed a map/dictionary, but additionally every object inherits some of the properties (key-value pairs) from another object. That other object is called prototype.

例如：

var o = {
    x: 1
};

console.log(o.x === undefined);           // false, obviously
console.log(o.toString === undefined);    // false, inherited from prototype

最常见的是通过创建带有构造函数的对象来设置原型：

Most commonly a prototype is set by creating an object with a constructor function:

var d = new Date();
console.log(d.hasOwnProperty('getYear'));     // false, it's inherited

编辑：

以下是原型如何使用构造函数（它是一个在JS中进行OOP的方式）：

Here's how the prototype works using constructor functions (it's one of the ways to do OOP in JS):

// constructor function
// starts with capital letter, should be called with new
var Person = function (name, age) {
    // set properties of an instance
    this.name = name;
    this.age = age;
};

// functions to be inherited are in the prototype
Person.prototype.sayHello = function () {
    return this.name + ' is ' + this.age + ' old';
};

// new:
// - creates the object
// - sets up inheritance from prototype
// - sets the object as the context of the constructor function call (this)
var p = new Person('Jason', 27);

console.log(p.sayHello());

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