What is JavaScript engine?
[[File:V8 JavaScript engine logo 2.svg|thumb|V8 (JavaScript engine) logo]] A '''JavaScript engine''' is a program that runs [[JavaScript]] code. [[Web browser|Web Browsers]] often have a JavaScript engine. It can also be used outside of web browsers, such as running services in [[Node.js]] or apps in the electron framework. == Design == JavaScript was originally created as a [[scripting language]] to allow web pages to have changing, or dynamic, elements. Early Javascript engines were created as [[Interpreter (computing)|interpreters]], programs that simply read the script and execute the instructions without analyzing it any more. As JavaScript started being used more an more as a [[General-purpose programming language|general-purpose language,]] execution speed, or how quickly the code is run, became more important for JavaScript engines. In response, many engines, such as V8 (Used in [[Google Chrome|Chrome]] and [[Chromium (web browser)|Chromium]]) and SpiderMonkey (used in [[Mozilla Firefox|Firefox]]), started using Just-In-Time Compilation. In this method, it starts by [[Compiler|compiling]] all of the code to optimized [[machine code]], which is typically faster than interpretation, then running the result.<ref>{{Cite web|last=Doglio|first=Fernando|date=2020-08-12|title=The JIT in JavaScript: Just In Time Compiler|url=https://blog.bitsrc.io/the-jit-in-javascript-just-in-time-compiler-798b66e44143|access-date=2021-01-02|website=Medium|language=en}}</ref><ref>{{Cite web|title=A crash course in just-in-time (JIT) compilers – Mozilla Hacks - the Web developer blog|url=https://hacks.mozilla.org/2017/02/a-crash-course-in-just-in-time-jit-compilers|access-date=2021-01-02|website=Mozilla Hacks – the Web developer blog|language=en-US}}</ref> == References == <references />{{tech-stub}} [[Category:JavaScript]]