JavaScript Preliminary Summary

JavaScript is a kind of lightweight programming language, Web page of various interactive behavior, by JS implementation;

There are three ways to introduce JS:

A write directly inside the HTML tag

b written in the HTML file, written in <script>.........</script>, can be anywhere in the HTML file

C External JS file, like an external CSS file, the introduction of the syntax is <script src= "file name. js" type= "Text/javascript" ></script>

When a nesting occurs, you need to separate the double and single quotation marks;

JS three kinds of pop-up windows

Warning pop-up: Alert ("")

Confirmation dialog: Confirm pops up a dialog box to choose, click OK to return True, click Cancel to return to Flase

User-Selectable dialog box for content: Prompt

There are two ways to JS annotations:

Annotate a single line of content

/* * * Comment out multiple lines of content

JS Display the Data method:

document.write (""): content is displayed directly in the HTML

Console.log (): Browser's debug console

JS Syntax:

String with "" or "," means literally.

JS variables need to be defined as Var:

var a

A = 1, 2, 3 、、、 if the string is quoted

Operator:

Mathematical operators: +-*/% (take remainder) + + (plus 1)-(minus 1);

Relational operators: = = =! > >= < <=;

Logical operator:&& | | !；

Note: = is the meaning of the assignment

Conditional statement: If ELSE syntax

if (condition) {

If the condition is true, execute the code

}else{

Otherwise, execute the code here

}

You can add the else if setting multiple conditional statements;

Conditional statement, you can set nested, if (condition) {

if (condition) {

}else{

}

}

Switch statement: Syntax:

Switch(n variable ) {

Case 1:

Executing code block 1

break; (without break, you will always look down and execute the code with break)

< Span class= "hl-reserved" > Case 2:

< Span class= "hl-reserved" > Execute code block 2

< Span class= "hl-reserved" > br Eak

< Span class= "hl-reserved" > default: with case 1case 2 code }

< Span class= "Hl-code" > < Span class= "hl-reserved" > f or loop: syntax

< Span class= "hl-reserved" > < Span class= "Hl-code" >for (initial value (var a =1) , cyclic condition (a<=10), change condition (a++)) {

< Span class= "Hl-code" > < Span class= "hl-reserved" >　　 Write in the inner face to loop together

< Span class= "Hl-code" > < Span class= "hl-reserved" > }< /span> < Span class= "Hl-code" > < Span class= "hl-reserved" > outside Face only once

< Span class= "hl-reserved" > < Span class= "Hl-code" > You can add a for inside for: The loop is out, the loop is complete

for (initial value (Var a =1), loop condition (a<=10), change condition (a++)) {

for (var x =1; x<= 2; X + +) {

}

When the external for loop is once, wait for the inside for two times to complete the loop, the parent for the next time;

JavaScript Preliminary Summary