Javascript APIs with async properties

Image for post
Image for post

Getter properties are a great way to mask logic and expose what appears as static values. I find it extremely elegant to differentiate functionality from attributes. This logic may hide lazy calculations to be performed only on-demand, or it may hide logic that’s based on object’s, or even application state.

For example, a User object may have functionality like user.goOnline(), it should have attributes like user.isOnline. The check if a user is online should be performed on demand because this status may change from moment of instantiation to the moment of querying.

With the emerging of async/await in Javascript, it is now possible to create such lazy getters by pointing them to promises, creating more semantic APIs.

class User {
constructor(id) { ... }
goOnline() { ... }
addBadge(type) { ... }
get isOnline() {
.then(response => response.json())
.then(data => data.isOnline)
.catch(error => { throw error; });


Static object can also leverage this way of typing. An API object pointing to async properties may also appear more readable.

const api = {
get request() {
return new Promise(resolve => setTimeout(() => resolve({status: 200}), 1000))

When importing between modules — I feel the appeal is even greater.

module.exports = async () => {
const { request } = require('./api');
const { data } = await request;

And this just opens up endless sugary syntactic possibilities.

The following is a (simplified) real life example where I found using async getters made the final logic cleaner.
`git tag -a ${tag} -m "${await message}"`

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store