A Svelte component to format numbers

Photo by Nick Hiller on Unsplash

Let's develop a Svelte component that formats numbers in a human readable way.

Instead of 63476432, the component displays 64M. Here are a few more examples:

6	=>	6
63	=>	63
634	=>	634
6347	=>	6.3K
63476	=>	63K
634764	=>	635K
6347643	=>	6.3M
63476432	=>	63M

It supports different locales as well. Converting 63476432 looks as follows

ko-KR	=>	6348만
zh-TW	=>	6348萬
de-CH	=>	63 Mio.
ar-SA	=>	٦٣ مليون

How it's done

We leverage the Number.prototype.toLocaleString() method (docs). Thanks to that, the Svelte component becomes very basic:

<script>
  export let number;
  export let locale = "en";

  $: formattedNumber = number.toLocaleString(locale, {
    notation: "compact",
    compactDisplay: "short",
  });
</script>

<style>
  span {
    font-variant-numeric: tabular-nums;
  }
</style>

<span>{formattedNumber}</span>

It is important to make sure number is of type Number. If you pass a string, the toLocaleString method will not work as intended.

Typescript

I highly recommend you enable Typescript for your Svelte project (instructions) and refactor the FormattedNumber component as follows:

<script lang="ts">
  export let number: number;
  export let locale: string = "en";

  $: formattedNumber = number.toLocaleString(locale, {
    notation: "compact",
    compactDisplay: "short",
  });
</script>

<style>
  span {
    font-variant-numeric: tabular-nums;
  }
</style>

<span>{formattedNumber}</span>

Voilà, now the Typescript compiler makes sure you pass a Number.