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patchRequire.md
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# `patchRequire(vol[, unixifyPaths[, Module]])`
Patches Node's `module` module to use a given *fs-like* object `vol` for module loading.
- `vol` - fs-like object
- `unixifyPaths` *(optional)* - whether to convert Windows paths to unix style paths, defaults to `false`.
- `Module` *(optional)* - a module to patch, defaults to `require('module')`
Monkey-patches the `require` function in Node, this way you can make
Node.js to *require* modules from your custom filesystem.
It expects an object with three filesystem methods implemented that are
needed for the `require` function to work.
```js
let vol = {
readFileSync: () => {},
realpathSync: () => {},
statSync: () => {},
};
```
If you want to make Node.js to *require* your files from memory, you
don't need to implement those functions yourself, just use the
[`memfs`](https://github.com/streamich/memfs) package:
```js
import {vol} from 'memfs';
import {patchRequire} from 'fs-monkey';
vol.fromJSON({'/foo/bar.js': 'console.log("obi trice");'});
patchRequire(vol);
require('/foo/bar'); // obi trice
```
Now the `require` function will only load the files from the `vol` file
system, but not from the actual filesystem on the disk.
If you want the `require` function to load modules from both file
systems, use the [`unionfs`](https://github.com/streamich/unionfs) package
to combine both filesystems into a union:
```js
import {vol} from 'memfs';
import {patchRequire} from 'fs-monkey';
import {ufs} from 'unionfs';
import * as fs from 'fs';
vol.fromJSON({'/foo/bar.js': 'console.log("obi trice");'});
ufs
.use(vol)
.use(fs);
patchRequire(ufs);
require('/foo/bar.js'); // obi trice
```

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