JS Syntax Basics

The origin of JS, the beginning of the 95 to check the server verification form data and gradually developed.

JS composition, 1 core (ECMAScript) 2 Document Object Model (DOM) 3 Browser object Model (BOM)

JS is an interpretive execution, a weak type, object-based, event-driven, cross-platform scripting voice

Objects include date objects, string objects, mathematical objects, a series of objects

Weak types do not differentiate between integers and decimals (relative to other programming speech) variables can store any type

Event-driven: event-based, such as mouse over (hover), mouse click (click, mouse Right-click) out of focus button bounce event

OnLoad Load Event

Cross-platform: windows, Linus

JS Useful, animation, interactive, game

Introduction of JS

JS is a. js suffix for JavaScript

1. Internal writing

2. External introduction (to add src, i.e. JS path)

Put it in the head, or the body.

JS syntax

1 Single-line comment

Single-line Comment

2 Quick-level annotations

/*

* Multi-line Comment

*/

Basic JS Pop-up window practice

Alert (1)

Problem: Path problem

Type= "Text/javascript"

Do not differentiate between single and double quotation marks

The basic syntax of JS

Each statement ends with a semicolon;

Strictly case-sensitive;

All symbols are in the English IME state

Console.log (' Hello ')

No meaning for console output, only for debugging

Javasript Direct quantities and variables

Direct Volume: Data values for direct use

Variable: The amount that can be dynamically changed

var a

The variable is made up of alphanumeric underscores, ￥, and cannot begin with a number

Use the Hump naming method, the first word lowercase

Output variable cannot be quoted

Case-sensitive to avoid duplication with system keywords

+ Meaning

1. Operator +

2. Connector connection string

Conversion of data types

1. Display Type conversions use function conversions

Number (' 123 ');//convert string to digital Nan:not a

String (123);//Convert a number to a string

parseint (' 123 ');//Convert a string to a number

parseint (3.14);//reserved integer digits

2. Implicit conversions

Number and string passed + after connection type is string

+ ' 12 ';//to take integer operations

Converts a Boolean value to a number

True--1

false--0

Number, except 0 is true;

A string that is true except for the byte-free;

Get element

JS time onload (window.onload) page when loading is complete

Get page element document.getElementById (); document, Element

Binding of basic events

OnClick event, Onmouseover,onmouseout event

JS three major Process Control

1, sequential structure

2. Select structure

3 Cycle structure

JS Syntax Basics