如何检测 React 中的 Esc 键按下以及如何处理

Question

How do I detect Esc keypress on reactjs? The similar thing to jquery

$(document).keyup(function(e) {
     if (e.keyCode == 27) { // escape key maps to keycode `27`
        // <DO YOUR WORK HERE>
    }
});

Once detected I want to pass the info down components. I have 3 components out of which last active component needs to react to the escape key press.

I was thinking of a kind of registering when a component becomes active

class Layout extends React.Component {
  onActive(escFunction){
    this.escFunction = escFunction;
  }
  onEscPress(){
   if(_.isFunction(this.escFunction)){
      this.escFunction()
   }
  }
  render(){
    return (
      <div class="root">
        <ActionPanel onActive={this.onActive.bind(this)}/>
        <DataPanel onActive={this.onActive.bind(this)}/>
        <ResultPanel onActive={this.onActive.bind(this)}/>
      </div>
    )
  }
}

and on all the components

class ActionPanel extends React.Component {
  escFunction(){
   //Do whatever when esc is pressed
  }
  onActive(){
    this.props.onActive(this.escFunction.bind(this));
  }
  render(){
    return (   
      <input onKeyDown={this.onActive.bind(this)}/>
    )
  }
}

I believe this will work but I think it will be more like a callback. Is there any better way to handle this?

Answer 1

If you're looking for a document-level key event handling, then binding it during componentDidMount is the best way (as shown by Brad Colthurst's codepen example ):

class ActionPanel extends React.Component {
  constructor(props){
    super(props);
    this.escFunction = this.escFunction.bind(this);
  }
  escFunction(event){
    if(event.keyCode === 27) {
      //Do whatever when esc is pressed
    }
  }
  componentDidMount(){
    document.addEventListener("keydown", this.escFunction, false);
  }
  componentWillUnmount(){
    document.removeEventListener("keydown", this.escFunction, false);
  }
  render(){
    return (   
      <input/>
    )
  }
}

Note that you should make sure to remove the key event listener on unmount to prevent potential errors and memory leaks.

EDIT: If you are using hooks, you can use this useEffect structure to produce a similar effect:

const ActionPanel = (props) => {
  const escFunction = useCallback((event) => {
    if(event.keyCode === 27) {
      //Do whatever when esc is pressed
    }
  }, []);

  useEffect(() => {
    document.addEventListener("keydown", escFunction, false);

    return () => {
      document.removeEventListener("keydown", escFunction, false);
    };
  }, []);

  return (   
    <input />
  )
};

Answer 2

For a reusable React hook solution

import React, { useEffect } from 'react';

const useEscape = (onEscape) => {
    useEffect(() => {
        const handleEsc = (event) => {
            if (event.keyCode === 27) 
                onEscape();
        };
        window.addEventListener('keydown', handleEsc);

        return () => {
            window.removeEventListener('keydown', handleEsc);
        };
    }, []);
}

export default useEscape

Answer 3

You'll want to listen for escape's keyCode (27) from the React SyntheticKeyBoardEvent onKeyDown :

const EscapeListen = React.createClass({
  handleKeyDown: function(e) {
    if (e.keyCode === 27) {
      console.log('You pressed the escape key!')
    }
  },

  render: function() {
    return (
      <input type='text'
             onKeyDown={this.handleKeyDown} />
    )
  }
})

Brad Colthurst's CodePen posted in the question's comments is helpful for finding key codes for other keys.

Answer 4

React uses SyntheticKeyboardEvent to wrap native browser event and this Synthetic event provides named key attribute ,
which you can use like this:

handleOnKeyDown = (e) => {
  if (['Enter', 'ArrowRight', 'Tab'].includes(e.key)) {
    // select item
    e.preventDefault();
  } else if (e.key === 'ArrowUp') {
    // go to top item
    e.preventDefault();
  } else if (e.key === 'ArrowDown') {
    // go to bottom item
    e.preventDefault();
  } else if (e.key === 'Escape') {
    // escape
    e.preventDefault();
  }
};

Answer 5

Another way to accomplish this in a functional component, is to use useEffect and useFunction , like this:

import React, { useEffect } from 'react';

const App = () => {


  useEffect(() => {
    const handleEsc = (event) => {
       if (event.keyCode === 27) {
        console.log('Close')
      }
    };
    window.addEventListener('keydown', handleEsc);

    return () => {
      window.removeEventListener('keydown', handleEsc);
    };
  }, []);

  return(<p>Press ESC to console log "Close"</p>);
}

Instead of console.log, you can use useState to trigger something.

Answer 6

function handleEsc(event) {
    if (event.keyCode === 27) {
      close();
    }
  }

  useEffect(() => {
    window.addEventListener("keydown", handleEsc);
    return () => {
      window.removeEventListener("keydown", handleEsc);
    };
  }, []);

Answer 7

If you want to make this work directly in your component instead of a hook, or if like me you are using this in a hook that DOES NOT return a <Component this worked for me.

useEffect(()=>{
    document.addEventListener('keydown', (e) => {
      e.key === 'Escape' && setOpenState(false)
    })
    return () => {
      document.removeEventListener('keydown', (e) => e)
    }
  },[openState])

Answer 8

React Hook

const [add, setAdd] = useState(false);
useEffect(()=>{
        document.addEventListener("keydown", keydownFunction, false);
        return  () => { document.removeEventListener("keydown", keydownFunction, false); };
    }, []);
const keydownFunction =(event)=>{
        if (event.key === "Escape") {  setAdd(false); }
        if (event.key === "+") { setAdd(true); }) }
}