How to read and use one js function into another js file?

Answer 1

import them into a common html page

<script src=source1></script>
<script src=source2></script>

Answer 2

AJAX then....

var aj = new XMLHttpRequest();
aj.open("GET","location");
aj.send();
aj.onload = function() {
eval(this.responseText);
};

Answer 3

my prog is based on command line in desktop...not web based...