svelte-currency-input

A form input that converts numbers to localized currency formats as you type

Features

• Formats positive and negative values
• Leverages Intl.NumberFormat for localizing currency denominations and masking the input
• Simple API
• Minimal default styling, easy to customize

Usage

npm install @canutin/svelte-currency-input --save

<script lang="ts">
  import CurrencyInput from '@canutin/svelte-currency-input';
</script>

<CurrencyInput name="total" value={-420.69} locale="nl-NL" currency="EUR" />

How it works

When the form is submitted you get unformatted or formatted values from two <input />'s. This is more or less what <CurrencyInput /> looks like under the hood:

<div class="currencyInput">
  <!-- Unformatted value -->
  <input
    class="currencyInput__unformatted"
    type="hidden"
    name="total"
    value="-420.69"
  />

  <!-- Formatted value -->
  <input
    class="currencyInput__formatted"
    type="text"
    name="formatted-total"
    value="€ -420,69"
  />
</div>

API

Option | Type | Default | Description | ----------------- | --------------- | ----------- | ----------- | value | number | undefined | Initial value. If left undefined a formatted value of 0 is visible as a placeholder | locale | string | en-US | Overrides default locale. Examples | currency | string | USD | Overrides default currency. Examples | name | string | total | Applies the name to the input fields for unformatted (e.g [name=total]) and formatted (e.g. [name=formatted-total]) values | required | boolean | false | Marks the inputs as required | disabled | boolean | false | Marks the inputs as disabled | placeholder | string number null | 0 | A string will override the default placeholder. A number will override it by formatting it to the set currency. Setting it to null will not show a placeholder | isZeroNullish | boolean | false | If true and when the value is 0, it will override the default placeholder and render the formatted value in the field like any other value. Note: this option might become the default in future versions | autocomplete | string | undefined | Sets the autocomplete attribute. Accepts any valid HTML autocomplete attribute values | isNegativeAllowed | boolean | true | If false, forces formatting only to positive values and ignores --positive and --negative styling modifiers | fractionDigits | number | 2 | Sets maximumFractionDigits in Intl.NumberFormat() constructor used for formatting the currency. Supported digits: 0 to 20 | inputClasses | object | See below | Selectively overrides any class names passed | onValueChange | Callback | undefined | Runs a callback function after the value changes |

Styling

There are two ways of customizing the styling of the input:

1. Passing it your own CSS classes
2. Overriding the styles using the existing class names

You can override all of the class names by passing an object to inputClasses that has one or more of these properties:

interface InputClasses {
  wrapper?: string; // <div> that contains the two <input> elements
  unformatted?: string; // <input type="hidden"> that contains the unformatted value
  formatted?: string; // <input type="text"> that contains the formatted value
  formattedPositive?: string; // Class added when the formatted input is positive
  formattedNegative?: string; // Class added when the formatted input is negative
  formattedZero?: string; // Class added when the formatted input is zero
}

Usage (with Tailwind CSS as an example):

<CurrencyInput name="total" value="{420.69}" inputClasses={
  { 
    wrapper: "form-control block",
    formatted: 'py-1.5 text-gray-700',
    formattedPositive: 'text-green-700',
    formattedNegative: 'text-red-700'
  }
} />

Alternatively you can write your own CSS by overriding the default styles which use BEM naming conventions. To do so apply your styles as shown below:

<div class="my-currency-input">
  <CurrencyInput name="total" value="{420.69}" />
</div>

<style>
  /* Container */
  div.my-currency-input :global(div.currencyInput) { /* ... */ }

  /* Formatted input */
  div.my-currency-input :global(input.currencyInput__formatted) { /* ... */ }

  /* Formatted input when the it's disabled */
  div.my-currency-input :global(input.currencyInput__formatted:disabled) { /* ... */ }

  /* Formatted input when the value is zero */
  div.my-currency-input :global(input.currencyInput__formatted--zero) { /* ... */ }

  /* Formatted input when the value is positive */
  div.my-currency-input :global(input.currencyInput__formatted--positive) { /* ... */ }

  /* Formatted input when the value is negative */
  div.my-currency-input :global(input.currencyInput__formatted--negative) { /* ... */ }
</style>

Contributing

Here's ways in which you can contribute:

• Found a bug? Open a new issue
• Comment or upvote existing issues
• Submit a pull request

Developing

This package was generated with SvelteKit. Install dependencies with npm install, then start a development server:

npm run dev

# or start the server and open the app in a new browser tab
npm run dev -- --open

Integration tests

The component is tested using Playwright. You can find the tests in tests/svelte-currency-input.test.ts

To run all tests on Chromium, Firefox and Webkit:

npm run test

To run all tests on a specific browser (e.g. Webkit):

npx playwright test --project=webkit

Additional debug commands can be found on Playwright's documentation.