Transpiler and Polyfills

What is a Transpiler?

A transpiler is compiler-like software that transforms modern JavaScript code into older JavaScript code so that it can work on older browsers.

For example:

const something = value ?? false;

will be transformed into:

const something = value !== undefined && value !== null ? value : false;

Build tools like Vite can run transpiler like Babel automatically on file changes, and the transformed code can be served to the browser.

polyfills is a fancy way of saying that said function does not exist, and we have to write it ourselves.

A polyfill is a script that adds new features to JavaScript and can also modify existing language features.

Polyfills are useful when: