What JavaScript can do

Introduction to JavaScript Features

JavaScript programs are used to detect activities and react to user actions, such as when the cursor passes over a link, which becomes a different color, a form of reaction to the user's actions. JavaScript programs provide navigation Help for Web sites, scrolling information, dialog boxes, dynamic images, shopping carts, and more. JavaScript programs allow you to control the appearance of Web pages and to evaluate the effectiveness of user input, which eliminates the burden of the server by interacting with the server. JavaScript programs can also detect whether a user's computer has some plug-ins installed, and can download the required plug-ins from the appropriate site when needed.

JavaScript provides string-handling functions and regular expression support, using them to check the validity of e-mail, network addresses, credit card numbers, cell phone numbers, and so on. JavaScript is an interpretive program that provides a set of basic language widget blocks, such as variables, data types, conditional statements, loop statements, functions, objects, and so on. Through these component blocks, can complete the mathematical computation, the operation date and time, the analysis string, the operation array and the object and so on. JavaScript can also write and read cookie values and dynamically create HTML pages based on specific cookie values.

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Overall, the main functions of JavaScript are as follows:

Control the appearance and content of a document

Controlling the behavior of the browser

Interacting with users

Use cookies to read and write client state

Manipulating embedded Images

Of course, JavaScript is not omnipotent, it is limited to browser and HTML-related tasks, and in a restricted context, so JavaScript does not have independent languages (such as C + +, JAVA, VB) have some of the necessary features. JavaScript does not have the characteristics:

JavaScript does not have any image processing capabilities other than the ability to format and display HTML documents

Client JavaScript does not allow read and write files for security reasons

JavaScript does not support any network access features beyond the ability to allow browsers to download any URL-specific content.

JavaScript does not have any multithreading capabilities