Is there anyway you can inject the JS with a script tag at startup? I do some similar kinds of things where I create a URL that calls a django view and that views is returned as javascript. In the html it looks like this:
<script src="app/generated.js"></script>
And I simply return a valid piece of javascript from the server. Since it comes over as a script tag, the browser has no idea it was generated. It's how I handle user specific customization.
In my django app, I return the response as content type 'application/javascript'
Given this kind of example, you could simply inject a <script> tag into the page at a later point.
And the details: (Since I don't know the platform you are using, I'll do it in django which I feel is very readable.)
In Django, you have functions that are mapped to urls like this:
urls.py
url(r'^generated.js$', generate_javascript, name="generate-custom-js")
This line will cause the function generate_javascript to run if that URL is requested from the server. In that function, I authenticate the user, and lookup some things from the database. then I render the javascript for this customer via a template.
views.py
@login_required
def generate_javascript(request):
previous_scores = Scores.objects.get(user=request.user).order_by('-date_recorded')[0:10]
return render(request, 'generate.tpl.js', locals(), content_type='application/javascript')
Then you complete the template like this:
generate.tpl.js
var scores = [
{% for score in scores %}
{{ score.number }}{% if not forloop.last %},{%endif %}
{% endfor %}
];
When rendered, this template generates a "file" that looks like:
var scores = [
1,
2,
3,
4,
5
];
It's not the prettiest javascript you'll ever write, but it will parse and the browser doesn't care what it looks like.
Then in your index.html you have a line like
<script src="generated.js"></script>
