If I understood your question correctly then my answer is…

Here are three files test.js, script.js and index.html

test.js

var qrandom = Math.floor(Math.random() * (quotes.length));
function randomQuote()

{

document.getElementById('quote').innerHTML = quotes[qrandom];

}
randomQuote();

script.js

var quotes = [
    "Quote 1",
    "Quote 2"
]

and index.html

[blank file]

What you would do is add this code to the HTML page:

<script src="script.js"></script>
<script src="test.js"></script>
<div id="quote"></div>

Please tell me if I misunderstood your question.