Use a node-style require() to organize your browser code and load modules installed by npm.

browserify is a tool for compiling node-flavored commonjs modules for the browser.

Think of JavaScript. In the browser you don't have direct access to the file system. In Node.js you have. Same programming language. Different APIs.

Node.js code must be run by the node process, not the browser (the code must run in the server).

Modules using code that doesn’t exist in browsers such as process.env.NODE_ENV and forcing you to convert or polyfill it.

Some modules, like events or util, are built in to Node.js. If you want to include those (for example, so that your bundle runs in the browser), you may need to include rollup-plugin-node-polyfills.

Ways of delivering JavaScript source code

One thing that matters is if code uses browser-specific (example: Dom) or server-specific (example: filesystem) features.

This is a non-dom based javascript execution environment. It usually only contains the base javascript language spec libraries and objects along with modules to communicate with OS features (available through commonjs require).