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Javascript es6 modules example

Modules are very useful when we want to make more reusable code, for example when you want some function or variable to be used outside the current module, that's when you need to export a module, similarly you also can import a module in JavaScript, in this tutorial you will learn Javascript ES6 modules.

What is Javascript ES6 Module?

ES6 modules are basically JavaScript File, so when you write any function in any JavaScript file those are not accessible outside the file by default, unless you export them!

es6 module export

To export any variable or function outside the module you need to use export keyword, let's look at the example below.

Here I have created a simple JavaScript file with “wc.js ”, and written the following codes

export var welcomeMessage = 'Welcome to WTR';
 
export function greetingMessage() {
  return welcomeMessage;
}

Now above function and variable will be accessible in a new file.

es6 module import

Now you see how to import the above functionality in a new module (JavaScript file)

Notice in following code, We use require to import a module, and when we write require('./module-name'), that indicates that’s a new local module.

let _wc = require('./wc');
_wc.greetingMessage();

Above example was of importing the entire module, means if there are 10 functions were written with export, all function will be available in our new module.

You also can import one particular binding instead of entire module as an object.

In earlier example we have seen how to import module using require keyword, here we use import keyword to import a module.

import * as s from './sample.js'; //will import the entire module
import {Notify} from './sample.js'; // will import only specified function of that module

Now you may think why using two different approaches to import a module, require and import, at the end both does the same job but differently

Actually, require is used in Node.js and import for ES6, but there is no JavaScript engine for ES6, you may use Babel or Node or may be something similar. Now Babel converts import declaration to CommonJS, even Node runtime also use CommonJS.

So to simplify the difference, as per CommonJs syntax, it uses “require” and as per ES6 it uses “Import”.

You may read further to understand technical differences between CommonJS and ES6 modules.


ES6 Tutorial | JavaScript Examples