Home > Developer > JavaScript

JavaScript new Function (") and new function () {} instance

Source: Internet
Author: User
Tags anonymous constructor object object
Developer on Alibaba Coud: Build your first app with APIs, SDKs, and tutorials on the Alibaba Cloud. Read more ＞

Scenario One:

The code is as follows Copy Code
var yx01 = new function () {return "center"};
alert (YX01);

We run the story one code, and it returns "[Object Object]", which is equivalent to:

The code is as follows Copy Code
function Anonymous class () {
return "center";
}
var yx01 = new anonymous Class ();
alert (YX01);

Our code for scenario one is modified below:

The code is as follows Copy Code
var yx01 = new function () {return new String ("Center")};
alert (YX01);

We run and will find the return of the "center", which is why?
As soon as the constructor returns (return) a Reference object (array, object, function, etc.) to the new expression, it overrides the anonymous object created by new, and returns a primitive type (return) of the original type undefined), then returns the anonymous object created by new. (Thank you Lunatic_sun, describe more precise points)
Because the new string constructs an object, rather than a String, and the new string (x) takes an argument, then alert it returns x. So yx01 returns the object of the new String ("center"), and alert yx01 displays the "center of the circle."
Scenario Two:

The code is as follows Copy Code
var yx02 = function () {return "center"} ();
alert (yx02);

We run the story code and return to the "center of the Circle," which is equivalent to:

The code is as follows Copy Code
var anonymous functions = function () {return "center"};
yx02 = anonymous function ();
alert (yx02);

Obviously, YX02 returns the execution result value of the anonymous function, that is, the yx02 is: "Circle


instance

The code is as follows Copy Code

<! DOCTYPE html>
    <meta charset= "Utf-8"/>
    <title></title>
<body>
    < Script>
        var f = new Function (' x ', ' y ', ' return x + y; '); /equivalent to var f = function (x, y) {return x + y;}
        Console.log (f (1, 1));
        var str = ' {' id ': 108} ';
        Console.log ((New Function (' return ' + str)) ());//String to object

        f = new function () {return ' CA ';};
        Console.log (f);
       //equivalent
       /*function anonymous class () {
            return ' CA ';
       }
        f = new anonymous Class ();
        Console.log (f); */
        F = new function () {return new String (' Ca ');
        Console.log (f);
       //As soon as the new expression constructor Returns (return) a Reference object (array, object, function, etc.), Will overwrite the anonymous object created by new, if returning an original type (return is in fact the original type undefined), then return the anonymous object created by new
    </ Script>
</body>

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

Related Keywords:
php new function new instance date and time function in javascript function and not function function within function in javascript function inside function in javascript javascript define new array

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

What's Trending
Top 10 Tags
datastax versions naming convention zookeeper client class definition md5 microsoft sql server 2005 data structures exception handling error handling
Top 10 Keywords
microsoft download center down wordpress address url site address url wordpress address url windows installer 4 0 download 302 not found web address url definition site address url wordpress db2 integer mac os installation step by step pdf abbreviation for return

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

Get Started for Free

  • Sales Support

    1 on 1 presale consultation

    Chat Contact Sales

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

    Open a Ticket

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.

    Learn More