Performance impact on unused require in Node.js?

Question

I have been wondering if is there any impact on performance in Node.js when including multiple packages using require() and not using them anymore? I mean the situation when I, for example, require underscorejs and not touch it anymore:

var _ = require('underscore');

Doing so in C++ (unused includes) increases the compilation time. But since in JavaScript there is no compilation, is this any harmful? Is the required module loaded when I run the file or only when I use any function from that module?

Answer 1

An unused require will impact your application's startup performance a bit, as well as increase its memory footprint.

The required module is loaded whether or not you later reference the module, so it's worth removing if you're not actually using the module.