In short

Fast and elegant scripting language that runs inside the browser, although it can also run stand alone; it has a checkered history.

item info
types Markup, Program code
preferred ❎ not applicable
extensions .es, .js
related formats C, CPP, CSS, HTML, JAVA, JSX, Markdown, Pascal, Perl, Prolog, Python, Ruby, Scala, SGML, TeX, XHTML, XML, XSLT
wikipedia JavaScript


JavaScript or more formally ECMAScript or ES6 is a scripting language that has been developed in a web context, but that has evolved into a full-fledged programming language.


It used to be a rather ugly and slow scripting language, snippets of which were included in HTML pages to add interaction to elements on the page and to submit forms. In those times it had competitors such as VBScript and PerlScript.

When Google introduced the Chrome browser it included a Javascript engine that had a performance that was unheard of.

Nowadays JavaScript is a capable, performant, and neat language that runs inside the browser as well outside it, through Node.

Since 2015 JavaScript is undergoing extensive development in a backwards compatible way. In that year, ECMA Script 6, or more fondly, ES6 was standardized. Now, in 2019, nearly all of ES6 is nearly fully implemented in nearly all major browsers on nearly all platforms and form factors. See the details.

Despite the lack of implementation during the years 2015-2019, many websites have been developed with ES6, using Babel, a transpiler that converts ES6 into pre-2015 Javascript. By the same approach, newer, post-ES6 features can be used in applications.

Modern uses

Modern websites have taken a lot of advantage from modern JavaScript. There has been a tendency to move processing on the server to the client, which has lead to so-called Single Page Applications (SPA), where the whole website is generated dynamically inside the browser.

This poses new challenges for the archiving of websites in general.

For SPAs to work correctly and optimally, web-frameworks such as React and Angular and Vue are needed that supply basic functions in the information flow. These package require subpackages, and they in turn require subpackages, and the app has a whole needs a build framework such as WebPack to bundle everything together, often for a development scenario as well as a production scenario. A moderate SPA requires easily hundreds of packages. It is nearly a miracle that is works, and even a greater miracle that these SPAs tend to work in most browsers.

Like CSS, the JavaScript in an SPA tends to be uglified, i.e. compressed by removing all unnecessary whitespace and line-breaks and replacing all names by meaningless short names.


In order to archive a website that has been built as an SPA, one needs to archive the full build environment in its original organization. Care must be taken that the subfolder node_modules exists and contains all the dependencies used by the SPA and not much more.

See also