jQuery is a library for the JavaScript programming language, a set of tools for web development. With its help, the developer accesses different elements of the web page and manages its content. So you can change the page depending on the settings and actions of the user.

jQuery is written in JavaScript, a popular language for web applications and working with interfaces. The original purpose of the library was to make the language more flexible and user-friendly, so that it would be easier to develop websites.

The library is cross-platform and cross-browser. This means that it can be used in any operating system, and the code written in it supports all browsers. The only exception for the new versions are old browsers like Internet Explorer 6, but they are practically never used now.

jQuery is licensed by MIT, it’s free and open source. There are other projects: jQuery UI and jQuery Mobile. They can be considered as additional extensions to the main library, they are designed for complex interfaces and mobile development. The name reads “jQuery”.

What jQuery is used for
The library is used by frontend developers who create the visible part of websites and web applications. They are often programmers who maintain legacy code in long-running projects.

jQuery is used:

• to quickly link JavaScript to HTML elements.
• Work with CSS selectors.
• navigating the DOM-tree: traversing, searching for elements, changing them.
• Handling events on the page and reactions to them.
• implementing AJAX-approach in which a page communicates with the server in the background.
• Creating animations and visual effects on the web page.

Now jQuery has largely superseded other popular JavaScript frameworks and extensions. Therefore, the library is partly considered obsolete, and it is not often used in new projects. This has happened because new frameworks and language updates have implemented almost the same functionality that it has.

But jQuery has been relevant for many years since its introduction, and many projects have been written on it and are still supported today. Therefore, a novice web developer should have an idea about the library. It is likely that sooner or later he will come across the code in jQuery, especially if he will work on projects with a long history.