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https://github.com/kentor/invalidate-module
Removes a module and all of its dependents from the require cache
https://github.com/kentor/invalidate-module
hot-reloading node require-cache
Last synced: about 17 hours ago
JSON representation
Removes a module and all of its dependents from the require cache
- Host: GitHub
- URL: https://github.com/kentor/invalidate-module
- Owner: kentor
- License: mit
- Created: 2017-05-10T06:47:01.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2017-06-11T00:22:23.000Z (over 7 years ago)
- Last Synced: 2024-10-06T22:45:59.506Z (about 1 month ago)
- Topics: hot-reloading, node, require-cache
- Language: JavaScript
- Size: 9.77 KB
- Stars: 9
- Watchers: 4
- Forks: 1
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# invalidate-module
[](https://travis-ci.org/kentor/invalidate-module) [](https://www.npmjs.com/package/invalidate-module)
Removes a module and all of its dependents from the require cache, so that
subsequent requires of that module or any of its dependents will return new
copies.
Useful for implementing a hot-reloading environment for Node.js programs in
watch mode.
e.g. iterating on a static site generator that uses server side rendered
React components for templating.
## Install
```
npm install invalidate-module
```
## Usage
Start the module dependencies tracking by requiring `invalidate-module`.
```js
const invalidate = require('invalidate-module');
```
Call `invalidate()` with the absolute path of a module to remove it and its
dependents from `require.cache`.
```js
invalidate(require.resolve('./my-module'));
```
Note that you must provide the absolute path of the module, so use something
like [`require.resolve()`][r] or [`path.resolve()`][p].
Now the next time you call `require('./my-module')`, it will return a new copy
of `./my-module` instead of a cached copy.
## Example
Example when used with a watcher like [chokidar][c]:
```js
// watch.js
const chokidar = require('chokidar');
const invalidate = require('invalidate-module');
const path = require('path');
const watcher = chokidar.watch('*.js', { ignoreInitial: true });
require('./a');
watcher.on('all', (event, filename) => {
invalidate(path.resolve(filename));
require('./a');
});
```
```js
// a.js
require('./b');
console.log('this is module a');
```
```js
// b.js
console.log('this is module b');
```
Running `watch.js` will call `require('./a')` which prints:
```
this is module b
this is module a
```
If you make this change to `a.js` and save:
```js
// a.js
require('./b');
console.log('this is module a, version 2');
```
The watcher callback will fire and invalidate `a.js` so that `require('./a')`
loads the new version and this gets logged:
```
this is module a version 2
```
Because `b.js` is still in `require.cache`, the `require('./b')` does nothing.
If you make this change to `b.js` and save:
```js
// b.js
console.log('this is module b version 2');
```
`b.js` and its dependent `a.js` will be invalidated and re-running
`require('./a')` in the watch callback will log:
```
this is module b v2
this is module a v2
```
## Details
At the time of requiring this module, node's `require()` is monkey-patched so
that subsequent calls will add the caller module and the required module to a
graph. When you call `invalidate()` on a module, it deletes the module from
`require.cache` and then it uses the graph to get the module's dependents and
deletes them from `require.cache` as well.
## Debug
Running with env vars `DEBUG=invalidate-module` will log the modules that are
deleted from `require.cache`.
## Further Reading
- My [blog post][b] on this subject.
- [node-hot-reloading-boilerplate][n]
[b]: https://kentor.me/posts/node-js-hot-reloading-development/
[c]: https://github.com/paulmillr/chokidar
[n]: https://github.com/kentor/node-hot-reloading-boilerplate
[p]: https://nodejs.org/api/path.html#path_path_resolve_paths
[r]: https://nodejs.org/api/globals.html#globals_require_resolve