JavaScript returns a reference to the array function that created this object. Property constructor-JS Tutorial-php.cn

JavaScript returns a reference to the array function that created this object. Property constructor

黄舟

Release： 2017-11-04 10:19:14

Original

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Definition and Usage

The constructor property returns a reference to the array function that created this object.

Syntax

object.constructor

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Examples

Example 1

In this example, we will show how to use the constructor attribute:

<script type="text/javascript">

var test=new Array();

if (test.constructor==Array)
{
document.write("This is an Array");
}
if (test.constructor==Boolean)
{
document.write("This is a Boolean");
}
if (test.constructor==Date)
{
document.write("This is a Date");
}
if (test.constructor==String)
{
document.write("This is a String");
}

</script>

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Output :

This is an Array

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Example 2

In this example, we will show how to use the constructor attribute:

<script type="text/javascript">

function employee(name,job,born)
{
this.name=name;
this.job=job;
this.born=born;
}

var bill=new employee("Bill Gates","Engineer",1985);

document.write(bill.constructor);

</script>

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Output:

function employee(name, job, born)
{this.name = name; this.job = job; this.born = born;}

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Example & Description

[native code] in the following code indicates that this is the underlying internal code implementation of JavaScript, and code details cannot be displayed.

// 字符串：String()
var str = "张三";
alert(str.constructor); // function String() { [native code] }
alert(str.constructor === String); // true
 
// 数组：Array()
var arr = [1, 2, 3];
alert(arr.constructor); // function Array() { [native code] }
alert(arr.constructor === Array); // true
 
// 数字：Number()
var num = 5;
alert(num.constructor); // function Number() { [native code] }
alert(num.constructor === Number); // true
 
// 自定义对象：Person()
function Person(){
    this.name = "CodePlayer";
}
var p = new Person();
alert(p.constructor); // function Person(){ this.name = "CodePlayer"; }
alert(p.constructor === Person); // true
 
// JSON对象：Object()
var o = { "name" : "张三"};
alert(o.constructor); // function Object() { [native code] }
alert(o.constructor === Object); // true
 
// 自定义函数：Function()
function foo(){
    alert("CodePlayer");
}
alert(foo.constructor); // function Function() { [native code] }
alert(foo.constructor === Function); // true
 
// 函数的原型：bar()
function bar(){
    alert("CodePlayer");
}
alert(bar.prototype.constructor); // function bar(){ alert("CodePlayer"); }
alert(bar.prototype.constructor === bar); // true

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In order to expose the prototype object of the instance constructor, for example, if you write a plug-in, others will get the object you instantiated. If others want to extend the object, they can use instance. constructor.prototype to modify or extend the prototype object

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