To use the `pegjs` command, install PEG.js globally:
```console
$ npm install -g pegjs
```
To use the JavaScript API, install PEG.js locally:
```console
$ npm install pegjs
```
If you need both the `pegjs` command and the JavaScript API, install PEG.js both ways.
If you plan to use the `pegjs` command only in your `package.json`, it is suggested you install it locally only, as all locally installed packages that contain command line tools are available to it.