JS High Set Note Chapter III

Source: Internet
Author: User

Chapter III Data Type P25

1, var message; Age variable not yet declared

alert (message); "Undefined"

alert (age); Error generated

Alert (typeof message); "Undefined"

Alert (typeof Age)//"undefined"

2,var message; This is the declaration variable

var message = undefined; This is an explicit initialization of the variable message with the undefined value.

3, below, excerpt from http://www.cnblogs.com/yang-wu/archive/2012/10/31/2748944.html

alert (a); var a = 123;  Alert output is undefined

alert (a); a = 123;   This will be an error.

JS High Set Note Chapter III

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.