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Hooks are a new addition in React that lets you use state and other React features without writing a class. This website provides easy to understand code examples to help you learn how hooks work and inspire you to take advantage of them in your next project.

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useKeyPress

This hook makes it easy to detect when the user is pressing a specific key on their keyboard. The recipe is fairly simple, as I want to show how little code is required, but I challenge any readers to create a more advanced version of this hook. Detecting when multiple keys are held down at the same time would be a nice addition. Bonus points: also require they be held down in a specified order. Feel free to share anything you've created in this recipe's gist.

import { useState, useEffect } from "react";
// Usage
function App() {
  // Call our hook for each key that we'd like to monitor
  const happyPress = useKeyPress("h");
  const sadPress = useKeyPress("s");
  const robotPress = useKeyPress("r");
  const foxPress = useKeyPress("f");
  return (
    <div>
      <div>h, s, r, f</div>
      <div>
        {happyPress && "😊"}
        {sadPress && "😢"}
        {robotPress && "🤖"}
        {foxPress && "🦊"}
      </div>
    </div>
  );
}
// Hook
function useKeyPress(targetKey) {
  // State for keeping track of whether key is pressed
  const [keyPressed, setKeyPressed] = useState<boolean>(false);
  // If pressed key is our target key then set to true
  function downHandler({ key }) {
    if (key === targetKey) {
      setKeyPressed(true);
    }
  }
  // If released key is our target key then set to false
  const upHandler = ({ key }) => {
    if (key === targetKey) {
      setKeyPressed(false);
    }
  };
  // Add event listeners
  useEffect(() => {
    window.addEventListener("keydown", downHandler);
    window.addEventListener("keyup", upHandler);
    // Remove event listeners on cleanup
    return () => {
      window.removeEventListener("keydown", downHandler);
      window.removeEventListener("keyup", upHandler);
    };
  }, []); // Empty array ensures that effect is only run on mount and unmount
  return keyPressed;
}
import { useState, useEffect } from "react";
// Usage
function App() {
  // Call our hook for each key that we'd like to monitor
  const happyPress: boolean = useKeyPress("h");
  const sadPress: boolean = useKeyPress("s");
  const robotPress: boolean = useKeyPress("r");
  const foxPress: boolean = useKeyPress("f");
  return (
    <div>
      <div>h, s, r, f</div>
      <div>
        {happyPress && "😊"}
        {sadPress && "😢"}
        {robotPress && "🤖"}
        {foxPress && "🦊"}
      </div>
    </div>
  );
}
// Hook
function useKeyPress(targetKey: string): boolean {
  // State for keeping track of whether key is pressed
  const [keyPressed, setKeyPressed] = useState(false);
  // If pressed key is our target key then set to true
  function downHandler({ key }): void {
    if (key === targetKey) {
      setKeyPressed(true);
    }
  }
  // If released key is our target key then set to false
  const upHandler = ({ key }): void => {
    if (key === targetKey) {
      setKeyPressed(false);
    }
  };
  // Add event listeners
  useEffect(() => {
    window.addEventListener("keydown", downHandler);
    window.addEventListener("keyup", upHandler);
    // Remove event listeners on cleanup
    return () => {
      window.removeEventListener("keydown", downHandler);
      window.removeEventListener("keyup", upHandler);
    };
  }, []); // Empty array ensures that effect is only run on mount and unmount
  return keyPressed;
}
November 14, 2018
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