# JavaScript > JavaScript, often abbreviated as JS, is a programming language and core technology of the Web, alongside HTML and CSS. 99% of websites use JavaScript on the client side for webpage behavior.[^1] JavaScript, often abbreviated as JS, is a and core technology of the , alongside and [CSS](https://wiki.g15e.com/pages/Cascading%20Style%20Sheets.txt). 99% of websites use JavaScript on the client side for webpage behavior.[^1] ## History - 2025-05-22 - [A brief history of JavaScript | Deno](https://deno.com/blog/history-of-javascript) ## Footnotes [^1]: https://en.wikipedia.org/wiki/JavaScript