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ES6 Modules: How to use import and export in JavaScript

Last modified March 4th 2021 | GitHub Source Code [GitHub]

ES6 provides the ability to split JavaScript into multiple files (modules). These modules can then be imported & exported as required into other files. This allows developers to organise project with many different JavaScript files.

To better understand how modules work let’s create a simple project that uses imports and exports. To get started create the following files and folder structure:

|- index.html |- app.js |- /src |- location.js |- weather.js

Then add the following markup to the index.html file:

<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8" /> <title>Our Application</title> </head> <body> <div id="app"></div> <script type="module" src="app.js"></script> </body> </html>
Code language: HTML, XML (xml)

Notice the type="module" so that the browser treats the script as a module, it wont work without it.

Exporting

Before we can import we must first export the code from the weather.js and location.js files. In weather.js let’s create a weather() function with an export directive:

export function weather() { const temperature = "15c"; const conditions = "Sunny" return temperature + " " + conditions; }
Code language: JavaScript (javascript)

And in location.js we’ll export multiple variables by adding the desired members to the export directive:

const country = "Australia"; const state = "Victoria"; const city = "Melbourne"; export { country, state, city };
Code language: JavaScript (javascript)

Importing

Now in the app.js file we can import the external JavaScript.

import { country, state, city } from "./src/location.js"; import { weather } from "./src/weather.js";
Code language: JavaScript (javascript)

Once imported the code can be used just as it would if it existed in a single JavaScript file. To complete the project we’ll output the imported modules data into the index.html.

const getWeather = weather(); const currentWeather = "<h2>Weather " + getWeather + "</h2>"; const currentLocation = "<h1>" + country + " | " + state + " | " + city + "</h1>"; document.getElementById("app").innerHTML = currentLocation + currentWeather;
Code language: JavaScript (javascript)

You should see the following when index.html is viewed in a browser.

Note: Modules will only work in files served via http(s) not in the local file system (file:///).

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