True and False in JavaScript

Source: Internet
Author: User

Today, we encounter a problem, do the following code return TRUE or False? Please explain why

Console.log ([] = =![])

Ran in the browser and found the result to be true. Why is that? Then found the relevant information.

In JavaScript 0, "", NULL, Unbdefined,nan,false is False, other is true

if NULL false {Console.log ("true")}else{Console.log ("false")}

Print result is False

In particular, when [] and = = or! = is used, it is treated as "", and a non-null or undefined object (including []) is used in a Boolean expression and is treated as true. So! The result of [] is false. Then []==! [] is equivalent to "" ==false, so the result is true.

The following code validates:

// print True, stating that [] and = = are treated as "" when used if ([]==false// print false, description [] with = = Falseif// print True, description in logical operation [] Be treated as true // print False

True and False in JavaScript

Related Article

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.

A Free Trial That Lets You Build Big!

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

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

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

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