Refs and the DOM
Refs provide a way to access DOM nodes or React elements created in the render method.
In the typical React dataflow, props are the only way that parent components interact with their children. To modify a child, you re-render it with new props. However, there are a few cases where you need to imperatively modify a child outside of the typical dataflow. The child to be modified could be an instance of a React component, or it could be a DOM element. For both of these cases, React provides an escape hatch.
When to Use Refs
There are a few good use cases for refs:
Managing focus, text selection, or media playback.
Triggering imperative animations.
Integrating with third-party DOM libraries.
Avoid using refs for anything that can be done declaratively.
For example, instead of exposing open()
and close()
methods on a Dialog
component, pass an isOpen
prop to it.
Don't Overuse Refs
Your first inclination may be to use refs to "make things happen" in your app. If this is the case, take a moment and think more critically about where state should be owned in the component hierarchy. Often, it becomes clear that the proper place to "own" that state is at a higher level in the hierarchy. See the Lifting State Up guide for examples of this.
Note
The examples below have been updated to use the
React.createRef()
API introduced in React 16.3. If you are using an earlier release of React, we recommend using callback refs instead.
Creating Refs
Refs are created using React.createRef()
and attached to React elements via the ref
attribute. Refs are commonly assigned to an instance property when a component is constructed so they can be referenced throughout the component.
Accessing Refs
When a ref is passed to an element in render
, a reference to the node becomes accessible at the current
attribute of the ref.
The value of the ref differs depending on the type of the node:
When the
ref
attribute is used on an HTML element, theref
created in the constructor withReact.createRef()
receives the underlying DOM element as itscurrent
property.When the
ref
attribute is used on a custom class component, theref
object receives the mounted instance of the component as itscurrent
.You may not use the
ref
attribute on function components because they don't have instances.
The examples below demonstrate the differences.
Adding a Ref to a DOM Element
This code uses a ref
to store a reference to a DOM node:
React will assign the current
property with the DOM element when the component mounts, and assign it back to null
when it unmounts. ref
updates happen before componentDidMount
or componentDidUpdate
lifecycle methods.
Adding a Ref to a Class Component
If we wanted to wrap the CustomTextInput
above to simulate it being clicked immediately after mounting, we could use a ref to get access to the custom input and call its focusTextInput
method manually:
Note that this only works if CustomTextInput
is declared as a class:
Refs and Function Components
By default, you may not use the ref
attribute on function components because they don't have instances:
If you want to allow people to take a ref
to your function component, you can use forwardRef
(possibly in conjunction with useImperativeHandle
), or you can convert the component to a class.
You can, however, use the ref
attribute inside a function component as long as you refer to a DOM element or a class component:
Exposing DOM Refs to Parent Components
In rare cases, you might want to have access to a child's DOM node from a parent component. This is generally not recommended because it breaks component encapsulation, but it can occasionally be useful for triggering focus or measuring the size or position of a child DOM node.
While you could add a ref to the child component, this is not an ideal solution, as you would only get a component instance rather than a DOM node. Additionally, this wouldn't work with function components.
If you use React 16.3 or higher, we recommend to use ref forwarding for these cases. Ref forwarding lets components opt into exposing any child component's ref as their own. You can find a detailed example of how to expose a child's DOM node to a parent component in the ref forwarding documentation.
If you use React 16.2 or lower, or if you need more flexibility than provided by ref forwarding, you can use this alternative approach and explicitly pass a ref as a differently named prop.
When possible, we advise against exposing DOM nodes, but it can be a useful escape hatch. Note that this approach requires you to add some code to the child component. If you have absolutely no control over the child component implementation, your last option is to use findDOMNode()
, but it is discouraged and deprecated in StrictMode
.
Callback Refs
React also supports another way to set refs called "callback refs", which gives more fine-grain control over when refs are set and unset.
Instead of passing a ref
attribute created by createRef()
, you pass a function. The function receives the React component instance or HTML DOM element as its argument, which can be stored and accessed elsewhere.
The example below implements a common pattern: using the ref
callback to store a reference to a DOM node in an instance property.
React will call the ref
callback with the DOM element when the component mounts, and call it with null
when it unmounts. Refs are guaranteed to be up-to-date before componentDidMount
or componentDidUpdate
fires.
You can pass callback refs between components like you can with object refs that were created with React.createRef()
.
In the example above, Parent
passes its ref callback as an inputRef
prop to the CustomTextInput
, and the CustomTextInput
passes the same function as a special ref
attribute to the <input>
. As a result, this.inputElement
in Parent
will be set to the DOM node corresponding to the <input>
element in the CustomTextInput
.
Legacy API: String Refs
If you worked with React before, you might be familiar with an older API where the ref
attribute is a string, like "textInput"
, and the DOM node is accessed as this.refs.textInput
. We advise against it because string refs have some issues, are considered legacy, and are likely to be removed in one of the future releases.
Note
If you're currently using
this.refs.textInput
to access refs, we recommend using either the callback pattern or thecreateRef
API instead.
Caveats with callback refs
If the ref
callback is defined as an inline function, it will get called twice during updates, first with null
and then again with the DOM element. This is because a new instance of the function is created with each render, so React needs to clear the old ref and set up the new one. You can avoid this by defining the ref
callback as a bound method on the class, but note that it shouldn't matter in most cases.
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