e.keyCode is Deprecated: How to Fix Key Event Issues in JavaScript

If you’re working on a JavaScript project that involves handling keyboard events, you may have encountered an issue where e.keyCode no longer works. This is because e.keyCode has been deprecated and is no longer recommended for use in modern JavaScript. Instead, you should use e.key, which provides a more readable and maintainable way to detect key presses.

🔴 The Problem: e.keyCode is Deprecated

In older JavaScript code, you might have seen something like this:

document.addEventListener('keydown', function (e) {
if (e.keyCode === 37) {
console.log('Left arrow pressed');
} else if (e.keyCode === 39) {
console.log('Right arrow pressed');
} else if (e.keyCode === 38) {
console.log('Up arrow pressed');
}
});

While this used to work, modern browsers may display a deprecation warning in the console. Some may even stop recognizing e.keyCode altogether in the future.


✅ The Solution: Use e.key Instead

Instead of using numerical key codes, you should use the e.key property, which returns the actual key name as a string.

Here’s how you can update your code:

document.addEventListener('keydown', function (e) {
if (e.key === 'ArrowLeft') {
console.log('Left arrow pressed');
} else if (e.key === 'ArrowRight') {
console.log('Right arrow pressed');
} else if (e.key === 'ArrowUp') {
console.log('Up arrow pressed');
}
});

This updated code makes it much clearer which keys are being checked and ensures better compatibility with modern JavaScript standards.


🎮 Fixing a Paddle Movement Issue

If you’re working on a game (e.g., a Pong or Breakout-style game) and your paddle movement stopped working due to e.keyCode being deprecated, you can update your code as follows:

🚨 Old Code (Using e.keyCode)

document.addEventListener('keydown', function (e) {
if (e.keyCode === 37) {
movePaddleLeft();
} else if (e.keyCode === 39) {
movePaddleRight();
} else if (e.keyCode === 38) {
jumpPaddle();
}
});

✅ New Code (Using e.key)

document.addEventListener('keydown', function (e) {
if (e.key === 'ArrowLeft') {
movePaddleLeft();
} else if (e.key === 'ArrowRight') {
movePaddleRight();
} else if (e.key === 'ArrowUp') {
jumpPaddle();
}
});

🔥 Why You Should Switch to e.key

  • Better Readability – You don’t need to remember cryptic key codes. "ArrowLeft" is much clearer than 37.
  • Future-Proof – Since e.keyCode is deprecated, using e.key prevents potential issues in future browser updates.
  • Cross-Browser Compatibility – Modern browsers fully support e.key, making it a more reliable choice.

📌 Conclusion

If your key event handling code suddenly stops working or logs a warning about e.keyCode being deprecated, switch to e.key for better readability, maintainability, and future-proofing.

Make sure to replace numeric codes like 37, 38, and 39 with their respective key names: 'ArrowLeft', 'ArrowRight', 'ArrowUp'. Y