Create a Modal Route with React Router
Introduction
Modals present a tricky situation for many applications. Are they a route? Are they just presenting info? Do users need to get back to whatever they’re presenting?
Regardless of the situation in React most modals are presented by toggling a piece of state. However on a refresh that state will no longer exist so the modal will close. The only mechanism for storing state that is shareable across users is via the URL. Let’s explore how to create a modal, and how we can go about turning into a route while not un-rendering the current route.
Setup Routes
So we need to setup our app routes. We’ll go with a 2 page app. The first is a home route, the second is a route to the Profile page. The Switch route will render the first route that is matched. This is all a very generic setup. One thing to point out is that there is no exact flag set on our /profile route.
So that means our profile route will match anytime you hit /profile or anything beyond that like /profile/edit.
Pages
The 2 pages above are React components with links.
Here we have a link to the Edit Profile “page” that will be our modal. This isn’t a valid link just yet as there is no to prop, but we'll get there.
Create a Modal
Rather than focusing on a specific Modal we’ll create a reusable one. We’ll be using createPortal from react-dom. We don't want to render to document.body so in our index.html we'll add another div to render to which we'll give an id of modal_root.
createPortal will render React provided, to a different place in the DOM and ensure that all appropriate context is passed along as well. Think of it as a "transport this HTML somewhere else". This allows for you to render something that makes sense hierarchically but functionally needs to exist somewhere else in the DOM.
The wrapping div will apply our styling, so it will be a fixed div covering the screen with a dark background. Upon click it will call a passed in onClick method which later we'll use for closing the modal.
We pass in our children which means any React that we want will be rendered in our modal, and transported to modal_root.
Render Dynamic Subroute
Now that we have our modal, pages, and routes all setup let’s look at how to put it all together. Upon clicking an Edit Profile link you might want a modal to pop up that covers the existing page.
Being a modal route it doesn’t make sense for a top level route, and because it’s dealing with the profile it makes sense to colocate this route. This is the power of React Router and its ability to render routes anywhere.
The concept is that a Route takes a path. If that Route is rendered and the path is matched then the supplied React will render.
Generally routes are thought of as full pages when in fact it could control a full page, or a small component. An example of this would be tabs. You may have multiple tabs on a page but want people to navigate to them. You can add in tab specific routes to that page. So one route to render the wrapping page, and any number of sub-tabs rendering with in that page. The URL will match to render the main outer page, and then the tab paths can be setup to render only when those URLs are visited.
Lets look at how this applies to our modal route. First let’s fix our Edit Profile link.
Rather than specifying /profile we can dynamically link to whatever page we are currently matched on. The match.url is supplied by React Router and is the path from the Route that is being rendered.
So because we had just /profile our match.url will always be /profile.
Even when we link to /profile/edit the Route that is rendering our ProfilePage only matched /profile. So our match.url will always be /profile.
So now our link can reference /profile dynamically, and if the top level route ever was changed our Edit Profile would still continue to work and we wouldn't need to search our entire codebase to fix the route.
Now that we’re on the ProfilePage we can render a new Edit Profile route, and just like our Link above we make it dynamic. We pass in our match.url along with the added /edit. When the user clicks or visits /profile/edit our Route will render the Modal.
Finally we add in an onClick to our Modal so when it's clicked we dismiss and push to the current match.url. Because we are in the ProfilePage and reference this.props of the profile page that match.url will reference /profile.
If you were to grab the props passed to the render={(props) => {}} function of route the props from that would the the props.match.url equal to /profile/edit.
End
I want to be clear, this works because the original /profile route that we rendered did not have an exact prop. If we added an exact prop this strategy would not work. It's important to think about how you design your components and routes.
If you needed to render other routes at the path /profile you could have the top level /profile not be exact like we have here, and then supply other more specific routes as subroutes inside of your ProfilePage. You can add in all the necessary design, modal edit paths, and then other subroutes would render totally different components as necessary.
You can check out the code here https://github.com/codedailyio/ReactRouterModal and or check out the live demo.
Originally published at https://codedaily.io on July 12, 2019.
