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JavaScript Advanced Programming--01

Source: Internet
Author: User
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Chapter Javasript Introduction to the first section

1. What is JavaScript?

An object-oriented, interpretive programming language.

Features of the 2.JavaScript.

    • Loose sex
    • Object Properties
    • Inheritance mechanism (prototype based)

3.JavaScript Core

    • Core (ECMAScript)
    • Document Object Model (DOM)
    • Browser object Model (BOM)

Chapter II using JavaScript


1. Create an HTML page

<!DOCTYPE HTML><HTMLLang= "en"><Head><MetaCharSet= "Utf-8"/><title>The first page</title></Head><Body><H1>Hello World</H1></Body></HTML>

2.<script> Label parsing

    • Defer----Specifies whether to defer execution of the script until the page loads.
    • SRC----Specifies the URL of the external script file.
    • Type----Specifies the MIME type of the script.
    • CharSet----Defines the character encoding used in the script. Not supported.

Some problems with 3.JS code embedding

Smooth degradation, JavaScript not supported

< NoScript > You do not have JavaScript enabled. </ NoScript >

Chapter III syntax, keyword reserved words and variables

1. Grammatical composition

    • Case sensitive
    • Identifiers: Variables, functions, names of properties, or parameters of a function
    • Comments//Single Line/* * * Multiple lines
    • Direct volume (literal)
    • Expressions for array literals and object literals are also supported by {x:1,y:2},{1,2,3,4,5}

2. Keywords and reserved words

3. Variables

Fourth Chapter data types

Simple data types: Undefined,null,boolean,number and string

Complex data type: Object

1.typeof operator

    • objects or null----object
    • Functions------function (not data type)

2.Undefined type

    • There is only one value, that is, the special undefined
    • Declaring a variable with VAR, but not initializing it
    • It is not necessary to assign a variable to undefined

3.Null type

    • There is only one value, that is, the special null
    • It represents an empty object reference (pointer)
    • If you define variables to be used in the future to save objects, it is best to initialize
    • Undefined is derived from Null,alert (undefined==null)//true

4.Boolean type

A Boolean value of false for the following conditions

    • Empty string
    • 0 and Nan
    • Null
    • Undefined

5.Number type

Floating-point range

Number.min_value~~~number.max_value

    • Alert (IsNaN (NaN))---True
    • Alert (number (TRUE))---1
    • Alert (number (NULL))---0
    • Alert (number (undefined))----false

JavaScript Advanced Programming--01

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