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Asked: 2024-09-27T19:13:14+05:30 In:

How to efficiently handle key hold events with delayed, continuous actions in JavaScript?

So, I’ve been diving into some JavaScript tricks lately and came across this really interesting challenge that involves event handling and intervals. The way we handle events like `onkeydown` can really affect how our applications behave, right? Anyway, I’m trying to come up with a function that responds to key presses, but I want to make it as efficient and concise as possible—like a little challenge to myself.

Here’s the thing: I want to implement a way to start an action every time a key is held down. But, instead of firing a ton of events every millisecond while holding the key, I’d like to limit the action to execute every few hundred milliseconds, or something like that. You know, just to keep it smooth without overwhelming the browser or the user.

Let’s say I want to create a simple game where pressing a key makes a character move. If the user holds down the key, I want the character to move continuously, but only after a short delay when the key is first pressed. Ideally, after that initial delay, it continues to move at a consistent interval. The tricky part is stopping the movement when the key is released. I’ve read some snippets about using `setInterval` and `clearInterval` for this, but it still feels like there must be some clever JavaScript tricks that can make the code more concise and elegant.

So, my question is: How would you go about crafting this functionality in a neat and efficient way? Would you use an arrow function or any other syntactic sugar to keep things short? And, of course, if you can share any snippets or examples that showcase your approach, that would be awesome! I’m really curious to see how others tackle this problem creatively, especially if there’s a way to condense the usual boilerplate into something really compact. Can’t wait to see your solutions and ideas!

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    2 Answers

    1. Key Press Movement Example


    2. To create a smooth and efficient character movement in response to key presses, we can utilize a combination of event listeners and timers. Using setInterval and clearInterval allows us to control the frequency of the movement action without overwhelming the browser. Here’s a concise implementation using arrow functions that starts the movement after an initial delay when the key is pressed and continues at a consistent interval until the key is released. The code defines a moveCharacter function which is triggered every 200 milliseconds, following a 500 milliseconds delay upon the first key press:

      
const moveInterval = 200; // Movement interval in milliseconds
let moveTimer; // To hold the interval ID
const character = { x: 0, move: () => this.x += 1 }; // Mock character object for demonstration

const handleKey = (e) => {
    if (e.key === 'ArrowRight') {
        if (!moveTimer) {
            setTimeout(() => {
                character.move();
                moveTimer = setInterval(() => character.move(), moveInterval);
            }, 500);
        }
    }
};

const stopMoving = () => {
    clearInterval(moveTimer);
    moveTimer = null;
};

window.addEventListener('keydown', handleKey);
window.addEventListener('keyup', stopMoving);

      This code snippet creates a reusable method for handling key presses efficiently while ensuring that the character moves smoothly. By initiating a setInterval that repeatedly calls the move method of the character object, we create a clean logic flow for character control that reacts both to the key down and key up events. This format keeps the code concise and leverages modern JavaScript features to enhance readability and maintainability.

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