JavaScript base -6 JavaScript branching structure (if, if-else, else if, switch-case)

Source: Internet
Author: User
Tags case statement

First, Process Control Overview



Process Control of the program

-Program = data + algorithm

-Any complex program algorithm can be implemented by "order", "branch", "Loop" three basic program logic combinations

650) this.width=650; "src=" Http://s4.51cto.com/wyfs02/M02/7E/03/wKioL1b1AUfw0hZ9AACpC1gtV4A054.png "title=" Web.png "alt=" Wkiol1b1aufw0hz9aacpc1gtv4a054.png "/>


Overview of branching structures

-The program can execute certain statements selectively in different situations during the running process

650) this.width=650; "src=" Http://s5.51cto.com/wyfs02/M00/7E/03/wKioL1b1AkGT07dIAAEgU8byRXo291.png "title=" Web.png "alt=" Wkiol1b1akgt07diaaegu8byrxo291.png "/>



Second, if statement


Execution logic for an if statement

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/7E/06/wKiom1b1Akvyb0bqAAGBqU8o8FY316.png "title=" Web.png "alt=" Wkiom1b1akvyb0bqaagbqu8o8fy316.png "/>


If statement flowchart

650) this.width=650; "src=" Http://s1.51cto.com/wyfs02/M01/7E/03/wKioL1b1A3mA0uvRAAEqrhzKZKM104.png "title=" Web.png "alt=" Wkiol1b1a3ma0uvraaeqrhzkzkm104.png "/>

-A Boolean value is required by default in the IF decision

-If the value that appears is not a Boolean type, it is automatically converted

650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M00/7E/03/wKioL1b1BgXwe_AWAADAjP4urWE007.png "title=" Web.png "alt=" Wkiol1b1bgxwe_awaadajp4urwe007.png "/>


If statement block do not omit ' {} '

650) this.width=650; "src=" Http://s5.51cto.com/wyfs02/M01/7E/06/wKiom1b1BaqhSV2qAAHiwxkzj6Y084.png "title=" Web.png "alt=" Wkiom1b1baqhsv2qaahiwxkzj6y084.png "/>


Third, If-else statement


Execution logic for IF-ELSE statements

650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M02/7E/03/wKioL1b1CFmQAcOCAAGLXFrBcXs727.png "title=" Web.png "alt=" Wkiol1b1cfmqacocaaglxfrbcxs727.png "/>


Iv. else If statement


If-else Statement Nesting

650) this.width=650; "src=" Http://s1.51cto.com/wyfs02/M02/7E/03/wKioL1b1B2-C3wVoAAEV60J4XLM261.png "title=" Web.png "alt=" Wkiol1b1b2-c3wvoaaev60j4xlm261.png "/>


Else if statement execution logic

-in fact, the else if structure is a simple way to do if else nesting

650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M00/7E/03/wKioL1b1B7eimGwcAAEE4b4XUHk631.png "title=" Web.png "alt=" Wkiol1b1b7eimgwcaaee4b4xuhk631.png "/>

650) this.width=650; "src=" Http://s4.51cto.com/wyfs02/M02/7E/07/wKiom1b1B0SjBK8gAAF0fljaWfU989.png "title=" Web.png "alt=" Wkiom1b1b0sjbk8gaaf0fljawfu989.png "/>


V. Switch-case statements


Switch-case Statement Execution logic

-The Switch-case statement is a special per-point structure that can be executed from different program entrances depending on the value of an expression

650) this.width=650; "src=" Http://s5.51cto.com/wyfs02/M02/7E/03/wKioL1b1CqCjaqsXAACCUusN7T4447.png "title=" Web.png "alt=" Wkiol1b1cqcjaqsxaaccuusn7t4447.png "/>


Switch-case and break joint use

-Usually the case1, Case2 、...、 CaseN correspond to a completely different operation and can be used in conjunction with the break statement, exit the switch block after executing the complete statement, do not proceed with the following statement,

650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M02/7E/07/wKiom1b1CvTQFzu0AABqd1FMpbM077.png "title=" Web.png "alt=" Wkiom1b1cvtqfzu0aabqd1fmpbm077.png "/>


Switch-case Statements for branching

650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M00/7E/07/wKiom1b1C3nCTAYyAABg1QJ0kqA019.png "title=" Web.png "alt=" Wkiom1b1c3nctayyaabg1qj0kqa019.png "/>


Advantages of Switch-case

-Switch-case is often used in conjunction with break statements to implement branching functions

-The main difference between Switch-case and if-else when implementing branching functions is that

-Switch...case ... The structure is clearer and more efficient, but it is generally used only to specify that a variable is equal to a specific value within a range


Summary: This chapter covers the basics of JavaScript -6 JavaScript branching structure (if, if-else, else if, switch-case)



This article from the "Technical Exchange" blog, declined reprint!

JavaScript base -6 JavaScript branching structure (if, if-else, else if, switch-case)

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.