Saturday, January 9, 2021 - svelte | components

A Svelte component to format numbers

Instead of 63476432, the component displays 64M.

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=>63M
zh-TW=>63M
de-CH=>63M
ar-SA=>63M

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.

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