martialkonvi / node-babel-async-await

A minimal example of using async/await syntax in Node.js via Babel.

Node.js async/await example

This is a very simple example of how to get async/await working for Node.js. It may work in the browser also, but that is outside the scope of this project.

package.json - NPM configuration

Our NPM configuration is pretty minimal. Basically 2 required dependencies, and a third just for demonstration purposes:

{
  "private": true,
  "dependencies": {
    "babel-preset-latest-minimal": "^1",
    "babel-register": "^6",
    "node-fetch": "^1"
  }
}

• "private": true - Because we never want to publish this by accident, and it shuts up NPM warnings about required fields.
• babel-preset-latest-minimal - Gives us only what we need on top of Node.js to support the latest ES2015+ features, including async/await. If you're trying to support the browser, you'll need babel-preset-latest instead.
• babel-register - Makes it so that when we import a module, it is transformed by Babel before being interpreted.
• node-fetch - This is just here so that we have something truly asynchronous to demonstrate. It's just fetch() implemented in Node.js.

.babelrc - Babel configuration

Our Babel configuration is tiny, and just specifies which preset to use:

{
    "presets": ["latest-minimal"]
}

• "presets": ["latest-minimal"] - Tells Babel to use the babel-preset-latest-minimal preset we installed.

Makefile - Task configuration

We need to pass a couple of command-line options to node, so we're using make to take care of them for us:

run: node_modules
    node --harmony --require babel-register index.js

node_modules:
    npm install

• run: node_modules:
  • This is our default target, named run.
  • Execute it with make run, or just make.
  • It depends on the node_modules target. If node_modules does not exist, the node_modules target will be executed first.
  • node --harmony --require babel-register index.js:
    • node - Should be obvious.
    • --harmony - Enables all the ES2015+ features that node can support out of the box, leaving less for Babel to do.
    • --require babel-register - Loads the babel-register module before interpreting our entry point script, so that it can also be written in ES2015+.
    • index.js - The path to our entry point script.
• node_modules:
  • This target handles populating our node_modules directory.
  • We don't need to execute it directly, it's automatically taken care of when we execute make run or make.
  • npm install - Installs the NPM dependencies we defined in package.json.

TL;DR

Just run make to see it in action.

index.js - async/await demo

Comments are included in the source:

// Import node-fetch so we have something asynchronous to demonstrate with.
import fetch from 'node-fetch'

// A simple wrapper around fetch() to log the request and response.
async function fetchAndLog(uri) {
    console.log('Fetching ' + uri)

    // These two statements are asynchronous,
    // but look almost like synchronous code.
    const response = await fetch(uri)
    const responseText = await response.text()

    console.log('Received ' + responseText)
}

// It's not possible to use await at the top level, so we need a simple async
// function wrapper.
(async () => {
    // These two operations are executed in series, despite being asynchronous.
    await fetchAndLog('https://httpbin.org/get?request=a')
    await fetchAndLog('https://httpbin.org/get?request=b')

    // These two operations are executed in parallel, and execution resumes when
    // both are finished.
    await Promise.all([
        fetchAndLog('https://httpbin.org/get?request=c'),
        fetchAndLog('https://httpbin.org/get?request=d'),
    ])
})();

Other files

• node_modules - Node.js stores out dependencies here.
• .gitignore - Makes Git ignore node_modules.
• npm-shrinkwrap.json - Makes npm install faster by storing how the dependencies resolved.
• README.md - See the README.