JavaScript
The only language every web browser runs on its own, which is why anything that reacts on a page without reloading it is written in JavaScript.
Also known as JS ECMAScript
Definition
JavaScript started as the language for making a web page respond to a click. It now also runs on servers, phones and desktops, which means one team can build the whole product without switching language between the screen and the engine behind it. Its reach, not its elegance, is why it is the most widely used language in the world.
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