November 2, 2019

Closing Modals with the Back Button in a Vue SPA

I recently gave my first conference talk, titled "The Laravel Developer's Guide to Vue SPAs" at Laracon AU. I shared a variety of different solutions and techniques that I discovered while building GiftyDuck — a social wish list and gift reminder service, built with a Vue SPA front end and Laravel back end.

One of the most popular tips I shared is something I call the "Modal Back Router Hack", because it's easier to give a silly catchy name and demo it, rather than try to explain it.

Demo

When the modal dialog is open, pressing the back button closes it. On a multi-step modal dialog, the back button can even navigate backwards through the steps!

On most web apps, pressing the back button while a modal dialog is open will navigate to the previous page, rather than closing the modal. This can be very frustrating! It might not seem like a huge deal on a desktop app, but on a mobile, where a modal like this will often be full-screen, and with phones having back buttons and back gestures, I believe it's a huge user experience improvement.

Using Vue Router "Navigation Guards"

My first implementation of this used routes for each modal dialog and the steps within them, but I quickly discovered that having history entries and separate URLs for each step was quite clunky, especially when they depended on having state passed into and between them.

The solution that worked out best for me uses Vue Router "Navigation Guards", which are a bit like route middleware in Laravel.

Keep in mind that you you will need to register the navigation guard each time your modal dialog opens. My modal dialogs are instantiated each time they're opened, and destroyed when they're closed, so I'm using Vue component lifecycle hooks. If you're using v-show then you will probably want to add a watcher to the piece of state controlling it.

export default {
  created() {
    // This will be called when the component is instantiated

    this.$once('hook:destroyed', () => {
      // This will be called when the component is destroyed.
      // It has access to anything defined in the scope of our "created" method.
    })
  },

  destroyed() {
    // This is the same as the 'destroyed' hook registered above, except it does
    // not have access to anything defined locally within our 'created' hook.
  },
}

The navigation guard is registered by calling $router.beforeEach() and passing a closure. This closure will be called before any navigation takes place, such as clicking on a router link, or pressing the browser back button. In my modals I don't have any router links, so the browser back button is the only route navigation possible. The navigation guard is free to do whatever it wants, and then can decide whether or not the navigation will continue by using the next() callback that Vue Router passes to us.

this.$router.beforeEach((to, from, next) => {
  // Do stuff

  // Then
  next() // move on to the next hook in the pipeline. If no hooks are left, the navigation is confirmed.
  next(false) // abort the current navigation.
  next('/') // redirect to a different location.
})

In my case, the navigation guard is calling a back() method on my modal component, which determines which step we are on, and either goes back to the previous step, or closes the modal.

Because I don't want to ever go to the previous route while my modal is open, I always pass false to the next() callback.

The beforeEach() method returns an "unregister" function, which we can call when we want to remove our navigation guard. We need to make sure that we do this once the modal is closed, otherwise the navigation guard will continue to intercept and prevent all route changes.

All together, our modal component might look something like this:

export default {
  created() {
    const unregisterRouterGuard = this.$router.beforeEach((to, from, next) => {
      this.back()

      next(false)
    })

    this.$once('hook:destroyed', () => {
      unregisterRouterGuard()
    })
  },

  methods: {
    back() {
      // Go to the previous step, or close the modal
    }
  },
}

I think this is a pretty big user experience improvement and I think it would be cool to see more modal dialogs implementing this behaviour.

On the topic of modals, don't forget to handle focus management properly! In my talk, I mentioned vue-focus-lock. Be sure to check out the "WHY" section.

The full talk will be posted on the Laracon AU YouTube channel sometime before the end of the year, so be sure to subscribe to the channel and follow me on Twitter to be notified when it's available!