Javascript (JS) is a dynamic programming language used for website building, the creation of web apps, game development and much more. For many years it has been ranked as the most widely used programming language in the world. It should not be confused with Java, with which it has no real connection.

JS was created very early in the development of the internet by a programmer called Brandon Eich who worked for the now-defunct Netscape Communications. In 10 days, he devised a new scripting language which, after an uncertain start, became the tool that, more than any other, enabled the internet to grow and thrive. In 1997 the European Computer Manufacturers Association (ECMA) assumed responsibility for the standardisation of computing and JavaScript’s place was secure.

Web designers use HTML to define the structure and content of webpages and CSS to add styles and animations. These are known as mark-up languages. JavaScript is what enables the dynamic and interactive features and functionality, such as mathematical calculations, dropdown menus, colour changes, style declarations and the gathering of content from other websites, to name just a few.

How it Works

JavaScript is a client-side programming language. This means all the processing of the source code is performed in the site visitor’s browser and not on the server. It enables Javascript to function on a page after it has loaded without referring back to the browser. 

For example, JavaScript can check web forms and other information for errors before anything is submitted. This suits the internet’s dominant client-server model whereby users and websites communicate via centrally located servers rather than with each other.

The reduced server interaction limits traffic load on the server and the system allows for immediate feedback rather than having to reload pages all the time. It also allows for limitless interfaces that react to a hovering mouse or a keystroke and gives the facility for features such as drag and drop or sliders.

For security reasons, JavaScript does not support the reading or writing of files. It cannot be used for networking applications and it has no multiprocessor or multi-threading capability.