What is JavaScript?

Javascript is a client-side scripting language that is object- and event-driven and relatively secure. It is also a scripting language widely used in client-side Web development. It is often used to add dynamic functions to HTML web pages, such as Respond to various user operations.

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

JavaScript is a client-side scripting language that is object- and event-driven and relatively safe. It is also a scripting language widely used in client-side web development. It is often used to add dynamic functions to HTML web pages, such as responding to various user operations. JavaScript does not need to be compiled in advance. It runs in the browser and can perform data statistics on the client.

JavaScript can also be used in other situations, such as server-side programming. The complete JavaScript implementation consists of three parts: ECMAScript, Document Object Model, and Byte Order Notation.

Main functions

1. Embed dynamic text in HTML pages.

2. Respond to browser events.

3. Read and write HTML elements.

4. Validate data before it is submitted to the server.

5. Detect the visitor’s browser information. Control cookies, including creation and modification.

6. Server-side programming based on Node.js technology.

JavaScript script language has the following characteristics:

(1) Script language. JavaScript is an interpreted scripting language. Languages ​​such as C and C are compiled first and then executed, while JavaScript is interpreted line by line during the running of the program.

(2) Based on objects. JavaScript is an object-based scripting language that can not only create objects but also use existing objects.

(3)Simple. The JavaScript language uses weakly typed variable types and does not impose strict requirements on the data types used. It is a scripting language based on Java's basic statements and controls, and its design is simple and compact.

(4)Dynamic. JavaScript is an event-driven scripting language that can respond to user input without going through a Web server. When visiting a web page, JavaScript can directly respond to these events when the mouse is clicked, moved up or down, or moved in the window.

(5) Cross-platform. The JavaScript scripting language does not depend on the operating system and only requires browser support. Therefore, after writing a JavaScript script, it can be brought to any machine for use, provided that the browser on the machine supports the JavaScript scripting language. JavaScript has been supported by most browsers. [6] Unlike server-side scripting languages, such as PHP and ASP, JavaScript is mainly used as a client-side scripting language to run on the user's browser and does not require server support. Therefore, in the early days, programmers preferred JavaScript to reduce the burden on the server, but at the same time it also brought about another problem, security.

As servers become more powerful, although programmers prefer scripts running on the server to ensure security, JavaScript is still popular for its cross-platform and easy-to-use advantages. At the same time, some special functions (such as AJAX) must rely on JavaScript to be supported on the client side.

Recommended study: "javascript Advanced Tutorial"

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