CODEWITHSUNDEEP
reactjstypescript
Akshar Patel
Akshar Patel

Reputation: 5787

How to use refs in React with Typescript

I'm using Typescript with React. I'm having trouble understanding how to use refs so as to get static typing and intellisense with respect to the react nodes referenced by the refs. My code is as follows.

import * as React from 'react';

interface AppState {
    count: number;
}

interface AppProps {
    steps: number;
}

interface AppRefs {
    stepInput: HTMLInputElement;
}

export default class TestApp extends React.Component<AppProps, AppState> {

constructor(props: AppProps) {
    super(props);
    this.state = {
        count: 0
    };
}

incrementCounter() {
    this.setState({count: this.state.count + 1});
}

render() {
    return (
        <div>
            <h1>Hello World</h1>
            <input type="text" ref="stepInput" />
            <button onClick={() => this.incrementCounter()}>Increment</button>
            Count : {this.state.count}
        </div>
    );
}}

Upvotes: 308

Views: 559780

Answers (16)

Muhammad Usman
Muhammad Usman

Reputation: 173

FIRST ADD AN IMPORT

import React, { useRef } from "react";

THEN THIS

const studentCapacityRef = useRef<HTMLInputElement>(null);

OR THIS

const studentCapacityRef = useRef<HTMLAreaElement>(null);

OR THIS

const studentCapacityRef = useRef<HTMLDivElement>(null);

etc...

Upvotes: 7

ford04
ford04

Reputation: 74710

React.createRef (class comp.)

class ClassApp extends React.Component {
  inputRef = React.createRef<HTMLInputElement>();
  
  render() {
    return <input type="text" ref={this.inputRef} />
  }
}

React.useRef (Hooks / function comp.)

a) Use readonly refs for React-managed DOM nodes: 
const FunctionApp = () => {
  // note the passed-in `null` arg ----------------v
  const inputRef = React.useRef<HTMLInputElement>(null)
  return <input type="text" ref={inputRef} />
}

inputRef.current becomes a readonly property by initializing its value with null.

b) Use mutable refs for arbitrary stored values akin to instance variables: 
const FunctionApp = () => {
  const renderCountRef = useRef(0)
  useEffect(() => {
    renderCountRef.current += 1
  })
  // ... other render code
}

Note: Don't initialize useRef with null in this case - it would make the renderCountRef type readonly (see example). If you need to provide null as initial value, do this:

const renderCountRef = useRef<number | null>(null)

Callback refs (both)

// Function component example, class analogue 
const FunctionApp = () => {
  const handleDomNodeChange = (domNode: HTMLInputElement | null) => {
    // ... do something with changed dom node.
  }
  return <input type="text" ref={handleDomNodeChange} />
}

Note: String Refs are considered legacy and omitted for the scope of this answer.

Playground sample

Upvotes: 133

J&#246;cker
J&#246;cker

Reputation: 6768

For those looking on how to do it when you have an array of elements:

const textInputRefs = useRef<(HTMLDivElement | null)[]>([])

...

const onClickFocus = (event: React.BaseSyntheticEvent, index: number) => {
    textInputRefs.current[index]?.focus()
};

...

{items.map((item, index) => (
    <textInput
        inputRef={(ref) => textInputs.current[index] = ref}
    />
    <Button
        onClick={event => onClickFocus(event, index)}
    />
}

Upvotes: 4

JulienRioux
JulienRioux

Reputation: 3092

If you're using React.FC, add the HTMLDivElement interface:

const myRef = React.useRef<HTMLDivElement>(null);

And use it like the following:

return <div ref={myRef} />;

Upvotes: 40

MiF
MiF

Reputation: 678

If you wont to forward your ref, in Props interface you need to use RefObject<CmpType> type from import React, { RefObject } from 'react';

Upvotes: 2

Morlo Mbakop
Morlo Mbakop

Reputation: 3756

For typescript user no constructor required.

...

private divRef: HTMLDivElement | null = null

getDivRef = (ref: HTMLDivElement | null): void => {
    this.divRef = ref
}

render() {
    return <div ref={this.getDivRef} />
}

...

Upvotes: 2

apieceofbart
apieceofbart

Reputation: 2197

Since React 16.3 the way to add refs is to use React.createRef as Jeff Bowen pointed in his answer. However you can take advantage of Typescript to better type your ref.

In your example you're using ref on input element. So they way I would do it is:

class SomeComponent extends React.Component<IProps, IState> {
    private inputRef: React.RefObject<HTMLInputElement>;
    constructor() {
        ...
        this.inputRef = React.createRef();
    }

    ...

    render() {
        <input type="text" ref={this.inputRef} />;
    }
}

By doing this when you want to make use of that ref you have access to all input methods:

someMethod() {
    this.inputRef.current.focus(); // 'current' is input node, autocompletion, yay!
}

You can use it on custom components as well:

private componentRef: React.RefObject<React.Component<IProps>>;

and then have, for example, access to props :

this.componentRef.current.props; // 'props' satisfy IProps interface

Upvotes: 36

Jeff Bowen
Jeff Bowen

Reputation: 6162

If you’re using React 16.3+, the suggested way to create refs is using React.createRef().

class TestApp extends React.Component<AppProps, AppState> {
    private stepInput: React.RefObject<HTMLInputElement>;
    constructor(props) {
        super(props);
        this.stepInput = React.createRef();
    }
    render() {
        return <input type="text" ref={this.stepInput} />;
    }
}

When the component mounts, the ref attribute’s current property will be assigned to the referenced component/DOM element and assigned back to null when it unmounts. So, for example, you can access it using this.stepInput.current.

For more on RefObject, see @apieceofbart's answer or the PR createRef() was added in.

If you’re using an earlier version of React (<16.3) or need more fine-grained control over when refs are set and unset, you can use “callback refs”.

class TestApp extends React.Component<AppProps, AppState> {
    private stepInput: HTMLInputElement;
    constructor(props) {
        super(props);
        this.stepInput = null;
        this.setStepInputRef = element => {
            this.stepInput = element;
        };
    }
    render() {
        return <input type="text" ref={this.setStepInputRef} />
    }
}

When the component mounts, React will call the ref callback with the DOM element, and will call it with null when it unmounts. So, for example, you can access it simply using this.stepInput.

By defining the ref callback as a bound method on the class as opposed to an inline function (as in a previous version of this answer), you can avoid the callback getting called twice during updates.

There used to be an API where the ref attribute was a string (see Akshar Patel's answer), but due to some issues, string refs are strongly discouraged and will eventually be removed.

Edited May 22, 2018 to add the new way of doing refs in React 16.3. Thanks @apieceofbart for pointing out that there was a new way.

Upvotes: 324

Akshar Patel
Akshar Patel

Reputation: 5787

EDIT: This is no longer the right way to use refs with Typescript. Look at Jeff Bowen's answer and upvote it to increase its visibility.

Found the answer to the problem. Use refs as below inside the class.

refs: {
    [key: string]: (Element);
    stepInput: (HTMLInputElement);
}

Thanks @basarat for pointing in the right direction.

Upvotes: 17

user2662112
user2662112

Reputation: 1

I always do this, in that case to grab a ref

let input: HTMLInputElement = ReactDOM.findDOMNode<HTMLInputElement>(this.refs.input);

Upvotes: 0

lucavgobbi
lucavgobbi

Reputation: 122

To use the callback style (https://facebook.github.io/react/docs/refs-and-the-dom.html) as recommended on React's documentation you can add a definition for a property on the class:

export class Foo extends React.Component<{}, {}> {
// You don't need to use 'references' as the name
references: {
    // If you are using other components be more specific than HTMLInputElement
    myRef: HTMLInputElement;
} = {
    myRef: null
}
...
 myFunction() {
    // Use like this
    this.references.myRef.focus();
}
...
render() {
    return(<input ref={(i: any) => { this.references.myRef = i; }}/>)
}

Upvotes: 2

Dimitar Dimitrov
Dimitar Dimitrov

Reputation: 15158

Just to add a different approach - you can simply cast your ref, something like:

let myInputElement: Element = this.refs["myInput"] as Element

Upvotes: 0

Dzmitry Valadziankou
Dzmitry Valadziankou

Reputation: 1

From React type definition

    type ReactInstance = Component<any, any> | Element;
....
    refs: {
            [key: string]: ReactInstance
    };

So you can access you refs element as follow

stepInput = () => ReactDOM.findDOMNode(this.refs['stepInput']);

without redefinition of refs index.

As @manakor mentioned you can get error like

Property 'stepInput' does not exist on type '{ [key: string]: Component | Element; }

if you redefine refs(depends on IDE and ts version you use)

Upvotes: 0

varman
varman

Reputation: 11

class SelfFocusingInput extends React.Component<{ value: string, onChange: (value: string) => any }, {}>{
    ctrls: {
        input?: HTMLInputElement;
    } = {};
    render() {
        return (
            <input
                ref={(input) => this.ctrls.input = input}
                value={this.props.value}
                onChange={(e) => { this.props.onChange(this.ctrls.input.value) } }
                />
        );
    }
    componentDidMount() {
        this.ctrls.input.focus();
    }
}

put them in an object

Upvotes: -1

Tikall
Tikall

Reputation: 2631

Lacking a complete example, here is my little test script for getting user input when working with React and TypeScript. Based partially on the other comments and this link https://medium.com/@basarat/strongly-typed-refs-for-react-typescript-9a07419f807#.cdrghertm

/// <reference path="typings/react/react-global.d.ts" />

// Init our code using jquery on document ready
$(function () {
    ReactDOM.render(<ServerTime />, document.getElementById("reactTest"));
});

interface IServerTimeProps {
}

interface IServerTimeState {
    time: string;
}

interface IServerTimeInputs {
    userFormat?: HTMLInputElement;
}

class ServerTime extends React.Component<IServerTimeProps, IServerTimeState> {
    inputs: IServerTimeInputs = {};

    constructor() {
        super();
        this.state = { time: "unknown" }
    }

    render() {
        return (
            <div>
                <div>Server time: { this.state.time }</div>
                <input type="text" ref={ a => this.inputs.userFormat = a } defaultValue="s" ></input>
                <button onClick={ this._buttonClick.bind(this) }>GetTime</button>
            </div>
        );
    }

    // Update state with value from server
    _buttonClick(): void {
    alert(`Format:${this.inputs.userFormat.value}`);

        // This part requires a listening web server to work, but alert shows the user input
    jQuery.ajax({
        method: "POST",
        data: { format: this.inputs.userFormat.value },
        url: "/Home/ServerTime",
        success: (result) => {
            this.setState({ time : result });
        }
    });
}

}

Upvotes: 0

basarat
basarat

Reputation: 276235

One way (which I've been doing) is to setup manually : 

refs: {
    [string: string]: any;
    stepInput:any;
}

then you can even wrap this up in a nicer getter function (e.g. here): 

stepInput = (): HTMLInputElement => ReactDOM.findDOMNode(this.refs.stepInput);

Upvotes: 33

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