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Editor to share with you what is the core component of javascript, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

The core components of javascript are: 1, ECMAScript, providing language syntax and basic objects; 2, DOM (document object model), an application programming interface for XML but extended for HTML; 3, BOM (browser object model).

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

The three core components of JavaScript are: ECMAScript,DOM (document object Model) and BOM (browser object Model).

-ECMAScript

ECMA-262 does not refer to the web browser and specifies the components of the language, including syntax, type, language, keywords, reserved words, operators, and objects.

ECMAScript is the description of the language in which the standard defines all aspects of content.

Compatibility of ECMAScript:

Supports all "types, values, objects, properties, functions, and program syntax and semantics" described by ECMA-262.

The Unicode character standard is supported.

Add more "types, values, objects, attributes, functions" that are not described by ECMA-262. The new features in western Zhejiang described by ECMA-262 mainly refer to new objects and new properties of objects that are not specified in the standard.

Support the syntax of programs and regular expressions that are not defined in ECMA-262. That is, you can modify and extend the built-in regular expression syntax.

-DOM (document object Model)

The document object model DOM is an application programming interface (API) for XML but extended for HTML. DOM maps the entire page to a multi-level node structure. Each component of a HTML or XML page is some type of node, which in turn contains a different type of data.

In DOM, pages can generally be represented by a hierarchical node graph.

DOM level:

DOM1 became the recommended standard of W3C in October 1998. BOM1 consists of two modules, DOM core and DOM HTML.

DOM core: specifies how to map the XML-based document structure to simplify access to and manipulation of any part of the document.

DOM HTML: extends DOM core to add objects and methods for HTML.

DOM2 level extends the mouse and user interface event, scope, traversal and other subdivision modules on the basis of the original DOM, and increases the support for css through the object interface. Includes the following modules:

DOM Views (DOM view): defines an interface to track different document views.

DOM Events (DOM event): defines the interface between event and event handling.

DOM Traversal and Range (DOM traversal and scope): defines the interface for traversing and manipulating documents.

The DOM3 level further extends DOM, introducing the method of loading and saving modules to load and save documents in a unified way; the new DOM verification module is mainly the method of verifying documents.

-BOM browser object model

BOM handles browser windows and frames, and it is customary to count all browser-specific JavaScript extensions as part of BOM. Include the following:

The ability to pop up a new browser window.

The ability to move, zoom, and close browser windows.

A navigator object that provides details of the page loaded by the browser.

A location object that provides details of the page loaded by the browser.

A screen object that provides user resolution details.

Support for cookies.

Custom objects such as XMLHttpRequest and IE's ActionXobject.

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