Can I have an HTML number input's arrows jump different than its step attribute?

I have an <input type="number" step="1"> element for choosing font size. However, given the context of drawing on a large canvas, changing the number by 1 is barely noticeable. It would be more convenient for users if they could step up or down by 5 or 10 each time they click the arrow.

I still need to keep the step attribute at 1 because the input should remain valid even with fine-grained values. Is there a way to achieve this behavior, like the below (pseudo) jump attribute. I am open to Javascript solutions too but AFAIK there is no such event for when user clicks the arrows.

<input type="number" min="1" max="1000" step="1" jump="5" value="100" />

Solution

You could try this: The input event checks if the change in value matches the step value and adjusts it by the jump value accordingly.

Edit: In this case, to answer to your comment we will use a flag and add back the keydown event.

Add a condition to the input event listener to prevent that unwanted behaviour in case you manually change the value

document.addEventListener('DOMContentLoaded', () => {
  const input = document.querySelector('input[type="number"][min="1"][max="1000"][step="1"]');

  const jump = parseInt(input.getAttribute('jump'), 10);
  let previousValue = parseInt(input.value, 10);
  let isManualChange = false;

  input.addEventListener('keydown', (event) => {
    if (event.key === 'ArrowUp' || event.key === 'ArrowDown') {
      event.preventDefault();
      const currentValue = parseInt(input.value, 10);

      if (event.key === 'ArrowUp') {
        input.value = currentValue + jump;
      } else if (event.key === 'ArrowDown') {
        input.value = currentValue - jump;
      }

      previousValue = parseInt(input.value, 10);
      isManualChange = false;
    } else {
      isManualChange = true;
    }
  });

  input.addEventListener('input', (event) => {
    const currentValue = parseInt(input.value, 10);
    const step = parseInt(input.getAttribute('step'), 10);

    if (!isManualChange && Math.abs(currentValue - previousValue) === step) {
      if (currentValue > previousValue) {
        input.value = previousValue + jump;
      } else {
        input.value = previousValue - jump;
      }
    }

    previousValue = parseInt(input.value, 10);
  });
});

<input type="number" min="1" max="1000" step="1" jump="5" value="100" />