require-in-the-middle

Hook into the Node.js require function. This allows you to modify modules on-the-fly as they are being required.

Installation

npm install require-in-the-middle --save

Usage

const path = require('path')
const Hook = require('require-in-the-middle')

// Hook into the express and mongodb module
Hook(['express', 'mongodb'], function (exports, name, basedir) {
  const version = require(path.join(basedir, 'package.json')).version

  console.log('loading %s@%s', name, version)

  // expose the module version as a property on its exports object
  exports._version = version

  // whatever you return will be returned by `require`
  return exports
})

API

The require-in-the-middle module exposes a single function:

`hook = Hook([modules][, options], onrequire)`

When called a hook object is returned.

Arguments:

modules <string[]> An optional array of module names to limit which modules trigger a call of the onrequire callback. If specified, this must be the first argument. Both regular modules (e.g. react-dom) and sub-modules (e.g. react-dom/server) can be specified in the array.
options <Object> An optional object containing fields that change when the onrequire callback is called. If specified, this must be the second argument.
- options.internals <boolean> Specifies whether onrequire should be called when module-internal files are loaded; defaults to false.
onrequire <Function> The function to call when a module is required.

The onrequire callback will be called the first time a module is required. The function is called with three arguments:

exports <Object> The value of the module.exports property that would normally be exposed by the required module.
name <string> The name of the module being required. If options.internals was set to true, the path of module-internal files that are loaded (relative to basedir) will be appended to the module name, separated by path.sep.
basedir <string> The directory where the module is located, or undefined for core modules.

Return the value you want the module to expose (normally the exports argument).

`hook.unhook()`

Removes the onrequire callback so that it will not be triggerd by subsequent calls to require().

License

MIT