svelte-currency-input

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https://github.com/fmaclen/svelte-currency-input/assets/1434675/de131586-9c31-41c5-8a29-a0eae8556691

After doing some research I think there's multiple issues at play here.

I was able to "fix" the caret shifting issue by implementing Svelte's await tick() to determine when the DOM has finished updating instead of retrying:

// Wait for Svelte DOM updates
await tick();

// Defer caret position update
const endCaretPosition =
	startCaretPosition + formattedValue.length - previousFormattedValueLength;

// Set the caret position after DOM updates
inputElement?.setSelectionRange(endCaretPosition, endCaretPosition);

This solution worked okay for Chrome and Firefox but it was causing an infinite loop in Safari (WebKit) where the on:blur event was getting triggered constantly until the browser crashes.

This is likely caused by calling setFormattedValue() from multiple places:

• onMount()
• on:blur={setFormattedValue}
• $: value, setFormattedValue();
• At te end of setUnformattedValue()
• And inside setFormattedValue() we are also calling back setUnformattedValue()

The fact that the data flows in so many different ways makes me think that our overall implementation needs to be re-thought from the ground up.

For example, I'm not sure we should listen to an on:blur event, looking at react-currency-field the formatting is always applied as the user types and not after clicking outside of the input, which feels like a nicer UX.

For reference, Bits-UI has WIP implementation of a NumberInput component written in Svelte 5 (which lacks a lot of our current features) and applies formatting after clicking outside of the input.

Maybe this is a good excuse to start re-writing the library with Svelte 5's new syntax 🤔

Great progress! Personally, I think the formatting should occur everytime the user types a number or a punctuation sign, it feels more intuitive (even more if we wanted to use this input in a mobile environment).