How Does Javascript Run featured image

Javascript is a dynamic programming language also referred to as a scripting language. If you’re like me you are currently thinking to yourself  ‘What the hell does dynamic mean in javascript’? That question led to this blog post.

A dynamic programming language is a language that executes at runtime. Runtime is the timeframe in which a program is running. When you programme in javascript you are basically writing a set of instructions to tell the environment what to do. During the runtime, you can work with almost anything like creating new variables, change the type of a variable, creating new functions load more scripts and more. There are many different runtime environments for Javascript the most common one being the web browser.

Javascript Engines

Browsers have built-in Javascript interpreters that understand the instructions in a Javascript program. The interpreter is also known as the Javascript engine. Each browser has its own Javascript Engine for example Spider Monkey was the first Javascript Engine which powered Netscape Navigator and the more recent Firefox, Chakra is used by Edge and Internet Explorer and V8 is the engine open-source solution for Google Chrome.


The job of the Javascript engine is to parse and execute Javascript code. It takes the Javascript code in your programme and converts machine code so it’s optimized for the environment.  The Javascript uses its built-in compiler called JIT (just in time) compiler for the conversion. Not only does it improve your programmes performance but it can also monitor the code as its running watching for any changes. This process is also known as run-time compilation. All of this happens in the blink of an eye. Once the code is produced by the run-time compilation the engine gives you access to all of the Javascript data types, operators, objects and functions so they can be used in the browser.


This is a very high-level look at how Javascript runs. While the browser is one of the most common Javascript environments there are also other environments like Node.js being one of the most popular and most used.  You can find out more about node.js by visiting  You can also geek out further by reading up dynamic programming languages, javascript engines and JIT. Thank you for taking the time to read my post stay tuned into our blog for all the latest from Scaffold.