4 May 2017

Simulating Asynchronous Events

  • Vanilla JS
  • Vue
  • React

Page refreshes are so 2005. Single page applications (SPA) are the new hotness, and offer a variety of design challenges. One such challenge is letting users know what’s happening while a request (e.g., a form submission) does it thing. This play will give you the fundamentals needed to prototype such situations.


Let’s suppose you’re designing a SPA. You want to introduce a pattern where a button that triggers an asynchronous event behind the scenes shows a spinner for the duration of the request.


The key here is to understand the “states” in which our button will live.

In its default state, the button will show the text “Submit Form”. In its loading state, the button will hide that text and show a spinner instead.

And so, we can mark up our button accordingly, wrapping the “Submit Form” text in a span tag with the class label, and the spinner in a span tag with the class spinner.

<button class="bg-blue bn white tc h3 fw6 w-100 relative">
  <span class="label">Submit Form</span>
  <span class="spinner absolute top-1 bottom-1 left-0 right-0">
    <!-- fancy SVG spinner goes here  -->

For simplicity’s sake, we can choreograph the hiding of the label / display of the spinner by toggling the class is-loading on the parent button tag.

button .spinner {
  opacity: 0; // Hide the spinner by default
  transition: opacity .2s ease-out;
button .label {
  display: block; // Show the label by default
button.is-loading {
  .label {
    display: none; // Hide the label when button 'is-loading'
  .spinner {
    opacity: 1; // Show the spinner when button 'is-loading'

Now, we can use Javascript to trigger this choreography on click of our button.

Implementation — Vanilla JS (ES6)

Here’s the game plan:

  • Write a function named showSpinner. The function should do a few things:
    • Add the is-loading class to our button — kicking off the choreography described above.
    • Remove the is-loading class after a duration of two seconds
    • Set the disabled attribute on our button to true while the is-loading class is present, to prevent users from repeatedly triggering the sequence.
function showSpinner() {
  let button = this
  let isEnabled = !button.disabled; // Is the button enabled?

  if (isEnabled) { // If so
    button.disabled = true // Disable the button
    button.classList.toggle('is-loading') // Toggle the class

    setTimeout(() => { // And do the following after 2 seconds
      button.classList.toggle('is-loading') // Toggle the class
      button.disabled = false // Enable the button
    }, 2000)
  • Add a click event listener to our button which calls the showSpinner function.
// Thou shalt do my bidding when clicked
button.addEventListener('click', showSpinner)

See the Pen Asynchronous Events - Vanilla JS (ES6) by Matt Rothenberg (@mattrothenberg) on CodePen.

Implementation — Vue JS

Here’s the game plan:

  • Construct a Vue instance and add a data property called loading to represent our button’s loading state
new Vue({
  el: '#app',
  data: {
    loading: false // Button shouldn't spin by default :)
  methods: {
    // nothing to see here
  • Mark up our button, adding the following:
    • A @click directive to which we can eventually attach an event listener
    • A :disabled attribute that we can enable/disable the button as a function of the loading state
    • A :class directive so that we can dynamically toggle the is-loading class with respect to our loading state
  v-bind:class="{'is-loading': loading}"
  class="bg-blue bn white tc h3 fw6 w-100 relative">
  • Implement the submitForm method and add it to our instance’s methods property. Like in the previous example, this method should add the is-loading class and remove it after a duration of two seconds
  • Fortunately, and thanks to Vue’s two-way data binding, we no longer have to manually set our button’s disabled attribute since it’s a function of our instance’s state
methods: {
  submitForm: function() {
    let self = this;
    self.loading = true; // set the instance's loading state to true

    setTimeout(() => {
      self.loading = false; // set it to false
    }, 2000) // After two seconds

See the Pen Asynchronous Events - Vue JS by Matt Rothenberg (@mattrothenberg) on CodePen.

Implementation — React JS

Here’s the game plan:

  • Scaffold a React component (using the traditional class syntax) to represent our button
class SpinnerButton extends React.Component {
  constructor () {
    super ()

    this.state = { // Similar to Vue's 'data' property
      loading: false
  • Implement our component’s render method to appease the React gods. Note that we’re only adding the is-loading class when our state’s loading attribute is truthy.
render () {
  let buttonClass

  this.state.loading ? // Are you loading?
    buttonClass = 'is-loading' : // If so, add 'is-loading' class
    buttonClass = ''

      disabled={this.state.loading} // Disable if loading
      className={"bg-blue bn white tc h3 fw6 w-100 relative " + buttonClass}> // Dynamically add the 'is-loading' class
       {<!-- implementation details -->}
  • Add an onClick handler to our button, and implement the function it calls
<button onClick={this.submitForm.bind(this)}></button>
submitForm () {
  let self = this

  setTimeout(() => {
  }, 2000)
toggleSpinner () {
    loading: !this.state.loading

See the Pen Asynchronous Events - React JS by Matt Rothenberg (@mattrothenberg) on CodePen.