JS Basic syntax

JS: all called: JavaScript. is the scripting language in the Web page.

Code embedding:

<script type="text/javascript"></script>

Try to write it down.

Basic knowledge:

All the characters are in English half-width.

In most cases, a semicolon is added after the end of each statement.

Add a newline after each piece of code ends.

The program echoes (preceded by a parenthesis "(" There must be a parenthesis ending ")").

Comment Syntax:

/* * * Multiple lines of comments.

Single-line comment.

Output syntax:

Alert (Info): Popup message.

Confirm (info): POPs up a dialog box that interacts with the user.

Prompt (info): POPs up a Text dialog box to enter content.

Console.log (Info): output in console.

Data type:

The data is stored in the program, and the stored name is called a variable.

It is divided into strong type language and weakly typed language.

strongly typed languages : The data storage needs to be stored in the corresponding data type variables.

Parameters : Integer (integer) int

Single Precision fractional float

Double-precision Decimal double

Fractional decimal

Currency type Money

Character Char

Strings string

boolean bool (only two states) true false true.

Date Time type DateTime.

Weakly typed languages : When data is stored, the type is not distinguished (type Auto-conversion).

Variable definition:

var a=10

If a variable with a decimal or integer is defined, the value is written directly after the equal sign.

If you define a string variable, the value after the equals sign needs double or single quotation marks

e.g. a= "hello,world!"

type transition:Parse (the type that will be converted).

An operator expression:

mathematical operators : Plus +; minus-; multiply *; remove/; take the remainder%.

logical operators :&& and; | | or;! Non -.

comparison operators : judging whether equal = =;

Not Equal! = or <>.

Greater than >.

Less than <.

is less than or equal to <=.

Greater than or equal to >=.

Other:

concatenation between strings with +. E.g.:alert ("Hello" +aa+ "world" + "!").

Ternary operators:

A==b? " A equals B ":" A is not equal to B "

Determine if they are equal.

Write a Boolean data directly.

JS Basic syntax