What is JavaScript divided into?

JavaScript can be divided into three parts: core (ECMAScript), Document Object Model (DOM) and Browser Object Model (BOM); these three parts respectively describe the syntax and basic objects of JavaScript, and process web content. methods and interfaces and methods and interfaces for interacting with the browser.

The operating environment of this tutorial: Windows 10 system, JavaScript version 1.8.5, Dell G3 computer.

What is JavaScript divided into?

JavaScript consists of three parts. They are core (ECMAScript), Document Object Model (DOM), and Browser Object Model (BOM). These three parts describe the syntax and basic objects of the language, methods and interfaces for processing web content, and methods and interfaces for interacting with browsers.

1.ECMAScript (Core)

Note:

1. ECMAScript has no dependency on the web browser. The browser is just the host for the ECMAScript implementation. One of the environments

2. What is defined is only the basics of the language, such as some grammar, types, statements, keywords, reserved words, operators, objects...

3. The host environment provides The basic implementation and extension of the language, such as DOM

4, other host environments

Node: Server-side JavaScript platform

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2. DOM (Document Object Model)

1. Function

(1) Map the entire page into a multi-layer node structure

(2) Then Provides a set of methods for adding, deleting, modifying and checking these nodes (content)

2. DOM level

(1)DOM1

How DOM Core maps the XML-based document structure

DOM html adds objects and methods for html

(2)DOM2

Expands mouse and user interface events, range, traversal and other subdivision modules, through objects The interface adds support for css.

The details are as follows:

DOM view: defines the interface for tracking different document views

DOM event: defines the interface for events and event processing

DOM Style: defines an interface for operating element styles based on css

DOM traversal and scope: a. Defines an interface for traversing and operating the document tree b. Adds a new method to verify the document

( 3) DOM3

Introduces a method to load and save documents in a unified way

3. Note

An application programming interface targeted at XML but extended for HTML (API), not just for JavaScript, many other languages also implement DOM.

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3.BOM (Browser Object Model)

1. Function

Processing browser windows and frames

JS extension for browser operations

2.Specific functions

Function of popping up a new browser window

Function of moving, zooming and closing the browser window

Navigator object that provides browser details

Provides browser The location object of the detailed information of the loaded page

The screen object that provides the detailed information of the user's monitor resolution

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XMLHttpRequest -- ActiveXObject

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