n/global-require

require() loads a module synchronously. Inside a function, it reads from disk and blocks the first time that function runs, and a missing module throws then instead of at startup. It also hides what the file depends on.

A require() inside a function, an if, a try or any other block is reported. A require that the file declares itself isn't.

Configure#

Off by default. To turn it on:

[lint.rules]
"n/global-require" = "error" # or "warn"

Examples#

Reported:

function readConfig(file) {
  const fs = require("fs");
  return fs.readFileSync(file, "utf8");
}

if (process.env.DEBUG) {
  require("./debug");
}

Not reported:

const fs = require("fs");
const join = require("path").join;
const log = require("./log")("config");
const debug = process.env.DEBUG ? require("./debug") : null;

function readConfig(file) {
  return fs.readFileSync(file, "utf8");
}

At the top level, a require() inside an object or array literal, or after && or ||, is reported too. Put it in its own variable:

module.exports = {
  parse: require("./parse"),
};

const debug = process.env.DEBUG && require("./debug");

When not to use it#

Loading a heavy or optional module only when you need it is a good reason to call require() inside a function. Turn the rule off for that line.