What is the structure of JavaScript programs?

Editor to share with you what the structure of JavaScript programs, I believe that most people do not know much, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to understand it!

There are three kinds of program structures in JavaScript, which are: 1, sequential structure; the program is executed line by line from top to bottom by default. 2. Branch structure; selective execution is different according to the result of conditional judgment. 3. Loop structure; the program can execute the same code segment repeatedly and exit when it reaches the critical point.

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

Program structure in JavaScript

It is divided into three main categories:

Order: programs are executed line by line from top to bottom by default

Branch: according to the result of conditional judgment, the selective execution is different.

Loop: the program can execute the same code segment repeatedly and exit when it reaches the critical point

*

Example:

Requirements Analysis:

Var price=prompt ("please input the goods price:"); var accout=prompt ("please input the goods account:"); var money=prompt ("please input the goods money:"); var sum=parseFloat (price) * parseInt (accout); (sum > 500) & & (sum*=0.8); var change=money-sum;alert ("receivable" + sum+ ", change" + change); branch structure

1.if structure:

Syntax:

If (condition) {snippet of code executed only if the condition is met}

2.if else structure:

Syntax:

If (condition) {Code snippet that meets the condition} else {condition not satisfied}

3.else if structure

Syntax:

If (condition 1) {Code snippet that meets condition 1} else if (condition 2) {condition 2 satisfies} else if (condition 3) {condition 3 satisfies} else {all previous conditions are not satisfied}

4. Branched vs trinocular / short circuit

If it's just a return value-- > three eyes / short circuit

If the operation is complex-> branch structure

Short circuit logic:

Condition & operation: one thing, do as soon as you meet it, otherwise don't do it, only if the operation is simple.

Value 1 | | value 2: if the value 1 is valid, the value 1 is returned, otherwise the value 2 is returned.

Trinocular operation:

Trinocular operation: multiple values, judge according to conditions, choose more than one

Conditional expression? Expression 1: expression 2

If the result of the conditional expression is true (true), the code in expression 1 is executed, otherwise the code in expression 2 is executed.

5.switch structure

Syntax:

Switch (expression) {case value 1: code 1: case value 2: code 2: case value 3: code 3; "`default: default code snippet;}

Break: stop the execution of the current structure and jump out of the current structure

Continue: ending the current cycle and continuing the next cycle / / control can generally be replaced by negative conditions.

Switch: switch case is preferred when congruent comparison is the condition

Else if: in addition to congruent comparison, when you want to define conditions flexibly

Cyclic structure

Loop structure: let the program execute a piece of code repeatedly and stop the loop only when the critical condition is reached

3 elements:

1. Cycle condition: the condition to continue the cycle

two。 Loop variable: in a loop condition, a variable used as a comparison

/ / from what number to start, how much to increase or decrease at a time, to what end

3. Loop body: code snippets that are executed repeatedly

While cycle

Conditions of use: when the change law of cyclic variables is uncertain

Grammar

While (conditional) {cyclic body; iterative cyclic variable;}

Example:

Guessing game: the computer randomly generates a number of 0-100, the player guesses the size of the number, and gives the hint of guessing big and small, until the final guess is right!

Var n=parseInt (Math.random () * (100,0,1) + 0); / generate a random number var input= ""; while (inputcounting random numbers = "exit") {input=prompt ("you guess"); alert (input > n? "bigger": input