There is a third argument that is available for use on the addEventListener method, which lets us specify some handy options like the once property. You would have needed to create a function that will then handle the event and so it is also visible within the other lifecycle methods, such as componentWillUnmount. If we leave listeners to hang around without cleaning them up, there could be serious performance and unexpected behaviour issues for our application, so please treat this matter with extra caution. This is what you can expect from this article if you continue reading: Before we dive into the code and implementations, I want to clear out something that I feel is a bit misunderstood about adding events in React and JavaScript in general.

Note: This entry shows how to attach DOM events not provided by React (check here for more info). react-event-listener A React component for binding events on the global scope. - onceA Boolean indicating that the listener should be invoked at most once after being added.

I’ve attached 100 events to a document, and by pressing a button the title of that button was replaced with another title. Using Event Listeners in React is not something that we want to overuse in general. Here is how it would have looked like if we had some listeners on the window, document, and element objects inside the Event Listeners tab: If you take a closer look of this last screenshot, you will see that except for the additional event listeners on the click event, there are events called “contextmenu” and “auxclick,”; those are definitely not defaults, but custom events added from codesandbox.io to the global event namespace. render, defeating EventListener's shouldComponentUpdate, and triggering an update cycle where it removes its old This is good for integrations with other libraries such as jQuery. Even worse, it can be hard to trigger effects and state updates based on DOM events. It's using the React lifecycle to bind and unbind at the right time. Since I am using codesandbox.io for the examples, we can see some additional listeners attached there as well. When doing server side rendering, document and window aren't available. There are cases though where we would need something different: something more customized to our needs, something more flexible. In the majority of cases, that would be all that we need to pass a function to one of the Synthetic Event handlers that React exposes for us.

You should avoid passing inline functions for listeners, because this creates a new Function instance on every There are exceptions and cases where this is just not optimal.

The code snippet above shows you how to add a keydown event listener to the window. It's quite easy. The docs say that when we pass that option, it gets automatically removed after our listener has been triggered, so we don’t have to worry about cleanup. You can use a string as a target, or check that they exist before rendering