Two things:

1) Defining a function this way puts it in the global scope. We don't need to think about this too much because 
2) We should wrap this in a document.ready call. That'd look like:
```
$(document).ready(function() {
    // do JS here
}
```

This will prevent a race condition if the DOM isn't prepared yet for the JS to be run.

Wrapping it in a doc.ready will keep ```main_map_init()``` within the scope of the function passed in. Ultimately there will need to be better structure, but for now its fine.