JavaScript: Module export and import (browser and Node.js runtime)

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Browser runtime

1. Open a HTML file with js modules directly from default browser will throw an error. You need to create a local server with VSCode.
2. The script.js file has imported module should have an attribute type= 'module' when linking to HTML, the file has exported module doesn't need to be linked to HTML.
3. To export several functions, export {func1, func2...} or add export before declare the function
4. To import a function func and rename it to newfunc, import {func as newfunc} from 'path'
5. To export a function as default, use export {func as default} or simply export default func
6. To import a default value, import importfunc from path works the same with import { default as importedResources } from 'path'
7. object-destructuring in import. MDN Web Docs on object destructuring

const resources = {
  func1,
  func2
}
export default resources;

import resources from 'path'
const {func1, func2} = resources

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Node.js runtime

1. module.exports.func1 = func1 to export function1.
2. const func1 = require('./path') to import values. For built in module, no need to provide the path.
3. object-destructuring in import:

module.exports = {
  func1,
  func2
}

import way 1:
const func = require('path');
const func1Value = func.func1;
const func2Value = func.func2;

import way 2:
const {func1, func2} = require('path')