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Javascript is not es5. Es5 is a version of ECMAScript, and ECMAScript is an important part of javascript and the specification of JavaScript syntax, which describes the basic syntax (var, for, if, array, etc.) and data types of the language.

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

What is JavaScript?

JavaScript is a dynamically typed, weakly typed, prototype-based client scripting language used to add dynamic functionality to HTML pages. (well, what's the most annoying concept?)

Dynamic:

Determine the data type at run time. A variable does not need a type declaration before it is used, and usually the type of the variable is the type of the value to which it is assigned.

Weak class:

In the calculation, different types can be converted transparently and implicitly to the user, and even if the type is incorrect, the correct type can be obtained by implicit conversion.

Prototype:

The new object inherits the object (as a template) and shares its own properties with the new object, which is called a prototype. In this way, when the new object is instantiated, it can enjoy not only the properties defined at creation time and run time, but also the properties of the prototype object.

PS: the new object refers to the function, the template object is the instance object, and the instance object cannot inherit the prototype.

JavaScript consists of three parts: 1. ECMAScript (core)

As the core, it defines the components of the language: syntax, type, statement, keyword, reserved word, operator, object

Implementation of PS:* incompletely compatible

2. DOM (document object Model)

DOM maps the entire page to a multi-tier node result, and developers can easily delete, add, replace, or modify any node with the API provided by DOM.

PS:DOM also has a level, divided into DOM1, DOM2, DOM3, expanding a number of specifications and new interfaces.

3. BOM (browser object Model)

The browser object model that can access and manipulate browser windows is supported, and developers can control parts other than the pages displayed by the browser.

PS:BOM does not form a specification

What is ES5?

As the fifth version of ECMAScript (the fourth version is obsolete because of its complexity), browser support can be seen in the first picture, with the following added features.

EECMAScript version

In June 1998, ECMAScript version 2.0 was released.

In December 1999, ECMAScript version 3.0 was released and became a general standard of JavaScript and was widely supported.

In October 2007, the draft version 4. 0 of ECMAScript was released, with a significant upgrade to version 3. 0. Because the goal of version 4.0 is too radical, there are serious differences on whether to adopt the standard.

In July 2008, ECMA suspended the development of ECMAScript 4.0 and released a small portion of it involving existing functional improvements as ECMAScript 3.1. Soon after, ECMAScript 3.1 changed its name to ECMAScript 5.

In December 2009, ECMAScript version 5.0 was officially released.

In June 2011, ECMAScript version 5.1 was released and became the ISO international standard (ISO/IEC 16262 ISO/IEC 2011).

In December 2013, the draft version 6 of ECMAScript was released.

In June 2015, ECMAScript 6 released its official version and changed its name to ECMAScript 2015. Mozilla launched JavaScript 2.0 on the basis of this standard.

From then on, JavaScript will be named after the year, and the new version will be released in the form of "ECMAScript+ year".

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