Q:

How do I include a javascript library for reference in spine.js

I have an old javascript library with methods I need to use from within my spine app. How do I include it for use within spine?

A:

You need to include the library in your slug.json in the "libs" section like so:
{
  "dependencies": [
    "jqueryify",
    ...
  ],
  libs: [
    "path/to/old/javascript/file.js"
  ]
}

This will tell Hem to package files under "lib" first in your application.js. You should have access to the methods in your Spine classes. Make sure you include the extension (".js") on libs and path them relative to the root of your app. You can see the Hem docs for more info.

