JavaScript Engines:

These are a separate part of web browser / not apart of the browser engine. That helps of compiling JavaScript code into a binary for the computer to run.
Historically they where only interpreters. But now have the additional capability of a just-in-time (JIT) compilation for much faster performance on supported platforms.
Popular exsamples include:

Google's V8: Included with any Chromium based browser or framework. Node.js also uses it.
Mozilla's SpiderMonkey: used for Firefox and forks. GNOME Shell also uses it where JavaScript is used.
Apple's JavaScriptCore: Used in WebKit based browsers. Also known as Nitro. Started as a fork of KJS.
Microsoft's JScript: Used in IE before version 9. As well anything based on though early versions of IE.
Microsoft's Chakra: The successor to JScript used in IE 9+ (Vista+) to all versions of Edge Legacy (Windows 10).
KDE's KJS: used in KHTML.

If your computer is fast enough. It is recommended to disable JIT features of JavaScript Engines (fallback onto interpreter mode). Due to less chance of successful exploits/payloads against the Web Browser.

Source 1 | Source 2 | Source 3 | Date: January 20th 2025

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