The following works for me in Firefox and Chrome. In Firefox it even works from file:///
models/course.js
export function Course() {
this.id = '';
this.name="";
};
models/student.js
import { Course } from './course.js';
export function Student() {
this.firstName="";
this.lastName="";
this.course = new Course();
};
index.html
<div id="myDiv">
</div>
<script type="module">
import { Student } from "https://stackoverflow.com/questions/48211891/./models/student.js";
window.onload = function () {
var x = new Student();
x.course.id = 1;
document.getElementById('myDiv').innerHTML = x.course.id;
}
</script>