object.constructor

返回创建实例对象的 Object 构造函数的引用。注意，此属性的值是对函数本身的引用，而不是一个包含函数名称的字符串。该值为只读的原始类型，如1，true和"test"。

描述

所有对象都会从它的原型上继承一个constructor属性：

var o = {};
o.constructor === Object; // true

var o = new Object;
o.constructor === Object; // true

var a = [];
a.constructor === Array; // true

var a = new Array;
a.constructor === Array // true

var n = new Number(3
n.constructor === Number; // true

示例

打印一个对象的构造函数

以下示例创建一个原型，Tree，以及该类型的对象，即theTree。然后打印theTree对象的constructor属性。

function Tree(name) {
  this.name = name;
}

var theTree = new Tree('Redwood'
console.log('theTree.constructor is ' + theTree.constructor

打印输出：

theTree.constructor is function Tree(name) {
  this.name = name;
}

改变对象的 constructor

以下示例显示如何修改泛型对象的构造函数值。只有true, 1 和"test"不受影响，因为他们有只读的原生构造函数。这个例子也表明依靠对象的constructor属性并不总是安全的。

function Type () {}

var types = [
  new Array(),
  [],
  new Boolean(),
  true,             // remains unchanged
  new Date(),
  new Error(),
  new Function(),
  function () {},
  Math,
  new Number(),
  1,                // remains unchanged
  new Object(),
  {},
  new RegExp(),
  /(?:)/,
  new String(),
  'test'            // remains unchanged
];

for (var i = 0; i < types.length; i++) {
  types[i].constructor = Type;
  types[i] = [types[i].constructor, types[i] instanceof Type, types[i].toString()];
}

console.log(types.join('\n')

此示例显示以下输出：

function Type() {},false,
function Type() {},false,
function Type() {},false,false
function Boolean() {
    [native code]
},false,true
function Type() {},false,Mon Sep 01 2014 16:03:49 GMT+0600
function Type() {},false,Error
function Type() {},false,function anonymous() {

}
function Type() {},false,function () {}
function Type() {},false,[object Math]
function Type() {},false,0
function Number() {
    [native code]
},false,1
function Type() {},false,[object Object]
function Type() {},false,[object Object]
function Type() {},false,/(?:)/
function Type() {},false,/(?:)/
function Type() {},false,
function String() {
    [native code]
},false,test

规范

Specification	Status	Comment
ECMAScript 1st Edition (ECMA-262)	Standard	Initial definition. Implemented in JavaScript 1.1.
ECMAScript 5.1 (ECMA-262)The definition of 'Object.prototype.constructor' in that specification.	Standard
ECMAScript 2015 (6th Edition, ECMA-262)The definition of 'Object.prototype.constructor' in that specification.	Standard
ECMAScript Latest Draft (ECMA-262)The definition of 'Object.prototype.constructor' in that specification.	Living Standard

浏览器兼容性

Feature	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic Support	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)

Feature	Android	Chrome for Android	Edge mobile	Firefox for Android	IE mobile	Opera Android	iOS Safari
Basic Support	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)