JavaScript engine

The JavaScript engine is the program responsible for parsing and executing your JavaScript source code.

For example, if you have this code in a main.js file loaded by your web page:

console.log('Hello, world!');

When the browser loads the main.js file, it invokes the JavaScript engine (a program within the browser) telling it “hey, execute this code for me”.

Examples of JavaScript engines

• V8 (used in Chrome, Node.js, Deno)
• SpiderMonkey (used in Firefox)
• JavaScriptCore (used in Safari)
• Chakra (used in older versions of Edge)