What parts does javascript consist of?

Javascript consists of 3 parts: 1. ECMAScript, the core part of the js language, which describes the syntax and basic objects of the language; 2. Document Object Model (DOM), a web document operation standard; 3. Browser Object Model (BOM), fundamentals of client and browser window operations.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

A complete JavaScript implementation consists of the following 3 different parts:

• Core (ECMAScript): The core part of the language, which describes the language syntax and basic objects.

• Document Object Model (DOM): Web page document operation standard, describing methods and interfaces for processing web page content.

• Browser Object Model (BOM): The basis for client and browser window operations, describing the methods and interfaces for interacting with the browser. .

Web browsers are just one of the host environments for ECMAScript implementations. The host environment not only provides basic ECMAScript implementation, but also provides various extended functions.

The Document Object Model is the application programming interface (API) of HTML. DOM maps the entire document into a tree node structure to facilitate quick access and operation by JavaScript scripts.

Core (ECMAScript)

ECMAScript defined by ECMA-262 is an internationally recognized standard scripting language specification that has no dependency on web browsers. The ECMA-262 standard mainly stipulates that this language consists of the following components:

1. Grammar

2. Variables and data types

3. Keywords and reserved words

4.Operator

5.Control statement

6.Object

In 2009, ECMAScript version 5.0 was officially released. For a long time, JavaScript was used in accordance with the 5.0 standard. In 2015, ECMAScript 6 was released as an official version, officially called ECMAScript 2015. ECMAScript defines all properties, methods and objects of the scripting language. Therefore, you must follow the ECMAScript standard when coding web client scripts.

Document Object Model (DOM)

DOM (Document Object Model) is the application programming interface (API) for HTML and XML. DOM will plan the entire page into a document composed of node hierarchies. Each component in an HTML or XML page is a node of some type, and these nodes contain different types of data.

Browser Object Model (BOM)

IE 3.0 and Netscape Navigator 3.0 provide a feature - BOM (Browser Object Model), which can access and operate. Using the BOM, developers can move windows, change text in the status bar, and perform other operations not directly related to the content of the page.

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