Using NPM to manage dependencies in a Cordova Plugin

Recently in my tutorial Creating reusable js-module's in Cordova I explained how to create a <js-module> that can be shared across your plugin. But what if we want to create a <js-module> from a third party library? And what if we want to use a dependency manager for that library?

I recently attempted to do just that with npm and found that with the implementation of a pre-install hook I was able to get my node modules to install before the plugin and then reference them within my plugin.xml.

Here's how to do it!

I'm going to continue this tutorial from where

We will need to create a package.json file to list our node dependencies in. To do so open up your terminal and type in the following command.
```
 cd loader; npm init
```
For the sake of this tutorial you can select all of the default options.
I've chosen the Event Emitter 2 to add to our library. We will combine this with our ajax component later. To add the dependency to our plugin type the following command into your terminal.
```
 npm install --save eventemitter2
```

Next we need to update our plugin.xml with the reference to our newly installed library.

 <js-module name="EventEmitter2" src="node_modules/eventemitter2/lib/eventemitter2.js">
     <runs/>
 </js-module>

Since our EventEmitter2 library won't be available in our repository when user's install the plugin we need to add a Cordova hook that will run our npm install before the plugin installs.
```
 mkdir hooks; cd hooks; touch install_dependencies.js
```

Now open the newly created fileinstall_dependencies.js and copy the following javascript.

 module.exports = function (context) {
     var shell = context.requireCordovaModule('shelljs');

     shell.cd(context.opts.plugin.dir);
     shell.exec('npm install');
 };

To have the hook execute we need to add a <hook> node to our plugin.xml. Open up your plugin.xml file and add the following xml.
```
 <hook type="before_plugin_install" src="hooks/install_dependencies.js" />
```
It's important to note that the type value is required to determine the behaviour of the hook. You may see examples where the hook is installed in a directory with the name of it's type ie ./hooks/before_install/, however this convention is deprecated.
Finally all we need to do is reference our newly created <js-module> in another javascript component. I'm going to open the ajax.component.js we created in our previous project.
```
 var eventEmitter = require('cordova-plugin-ajax.eventEmitter');
```