How to load and use third-party javascript file?

Cocos Creator
#1

Hi,
In normal HTML/JavaScript I would do this:

<script src="Scripts/jquery-3.3.1.min.js"></script>
<script src="Scripts/jquery.signalR-2.1.0.min.js"></script>

then:

<script>
    $(function () {
    	// Start the connection.
    	$.connection.hub.start().done(function () {
             // some code
    	});
    });
</script>

(The $ sign comes from jQuery )
But in Cocos Creator I don’t know how to do that. I did download the jQuery file and imported as plugin, but how can I use it like the second part of above code?

Any help is much appreciated