You can try as follows:
//------ js/functions.js ------
export function square(x) {
return x * x;
}
export function diag(x, y) {
return sqrt(square(x) + square(y));
}
//------ js/main.js ------
import { square, diag } from './functions.js';
console.log(square(11)); // 121
console.log(diag(4, 3)); // 5
You can also import completely:
//------ js/main.js ------
import * as lib from './functions.js';
console.log(lib.square(11)); // 121
console.log(lib.diag(4, 3)); // 5
Normally we use ./fileName.js for importing own js file/module and fileName.js is used for importing package/library module
When you will include the main.js file to your webpage you must set the type="module" attribute as follows:
<script type="module" src="js/main.js"></script>
For more details please check ES6 modules