How to import a js file to another js in html project

Question

I am working on a html project. I have 2 js file like main.js and config.js. I have some default export in config.js. So I was using import statement in main.js while it is giving me error Cannot use import outside of a module. Is there anyway to import config.js inside main.js?

config.js file

export const config = {
    identityBaseURL : 'https://url1.azurewebsites.net/',
    tenantId : '1234',
}

the above code is my config that I exported from config.js and wanted to import in main.js

import config from './config.js';

The above line I am using to import my config file into main.js file but I am getting the error which is Cannot use import outside of a module.