Making Numbers Speak Your Language in JavaScript

Numbers are a universal language, but how they are formatted and presented can greatly impact user experience, especially in a global context. In web development, Intl.NumberFormat is the tool that allows you to format numbers in a way that's not only easy to read but also culturally sensitive. In this blog post, we'll dive into the world of Intl.NumberFormat and explore how it can help you speak your users' language when it comes to numbers.

Introduction to Intl.NumberFormat

To get started with Intl.NumberFormat, you need to create an instance of it, specifying the user's locale. Here's a basic example:

const formatter = new Intl.NumberFormat('en-US');

In this example, we create a formatter that formats numbers according to the English (United States) locale.

To format a number, simply call the format method of the formatter instance:

const formattedNumber = formatter.format(1234567.89);
console.log(formattedNumber); // "1,234,567.89"

The formattedNumber now contains a string representing the number 1234567.89 in the 'en-US' locale.

Customizing Number Formatting

One of the key features of Intl.NumberFormat is the ability to customize how numbers are formatted. You can achieve this by passing an options object when creating the formatter. Here are some common options you can use:

• style: You can choose between decimal (default), currency, percent or unit.
• notation: it determines how the number will be displayed. Possible values includes
  • standard: the default number format, and the only type that can be used with currencies
  • scientific: returns the order of magnitude of the number
  • engineering: returns the exponent of 10 if the number is greater than 999
  • compact: an abbreviated version e.g 1K instead of 1,000

new Intl.NumberFormat("en-GB", {
  notation: "standard",
}).format(1001246) // 1,001,246

new Intl.NumberFormat("en-GB", {
  notation: "scientific",
}).format(1001246) // 1.001E6

new Intl.NumberFormat("en-GB", {
  notation: "scientific",
}).format(100) // 1E2

new Intl.NumberFormat("en-GB", {
  notation: "engineering",
}).format(1001246) // 1.001E6

new Intl.NumberFormat("en-GB", {
  notation: "engineering",
}).format(100) // 100E0


new Intl.NumberFormat("en-GB", {
  notation: "compact",
}).format(1001246) // 1M

Intl.NumberFormat allows you to format numbers in four different ways namely

1. Decimals e.g. 3.14
2. Currency e.g. $340
3. Percent e.g. 3.14%
4. Unit e.g. 3.14 kg

Currency

Of course, the first thing you want to do is to set the style to currency, and now determine the currency type.

The following options applies to currency

• currency: specifies the type of currency that you want to use e.g. USD for U Dollars. The full list of the codes can be found here. This is required if the style is currency.
• currencyDisplay: Determines how the currency is represented, that is, as symbol (default to the locale e.g. $ or US$), narrowSymbol ($), code (USD) or name (US Dollars)
• currencySign: (standard or accounting) in most locale, negative numbers are preceded with - symbol. You can change it to accounting where negative numbers are surrounded by parentheses instead, following accounting standards

new Intl.NumberFormat("fr-FR", {
  style: "currency",
  currency: "EUR",
}).format(1837747) // 1 837 747,00 €


new Intl.NumberFormat("en-US", {
  style: "currency",
  currency: "EUR",
}).format(203325) // €203,325.00


new Intl.NumberFormat("en-GB", {
  style: "currency",
  currency: "GBP",
}).format(1001246) // £1,001,246.00

currencyDisplay

The locale will usually affect the way the currency are written, this can be override with currencyDisplay
It determines how the currency would be represented or written. It accept the following values

• symbol: the default value, uses the local symbol
• narrowSymbol: makes uses of symbol without any extra letters e.g. $ instead of $US
• name: uses the local name of the currency like dollars or pounds
• code: uses the ISO currency code

new Intl.NumberFormat("fr-FR", {
    style: "currency",
    currency: "USD",
}).format(1837747) // 1 837 747,00 $US

new Intl.NumberFormat("fr-FR", {
  style: "currency",
  currency: "USD",
  currencyDisplay: "narrowSymbol",
}).format(1837747) // 1 837 747,00 $


new Intl.NumberFormat("fr-FR", {
  style: "currency",
  currency: "USD",
  currencyDisplay: "name",
}).format(1837747) // 1 837 747,00 dollars des États-Unis


new Intl.NumberFormat("en-US", {
  style: "currency",
  currency: "USD",
  currencyDisplay: "name",
}).format(1837747) // 1,837,747.00 US dollars


new Intl.NumberFormat("fr-FR", {
  style: "currency",
  currency: "USD",
  currencyDisplay: "code",
}).format(1837747) // 1 837 747,00 USD

currencySign

This determines how negative numbers are represented.

• standard: the default way of representing negative numbers, that is, -200
• accounting: this uses accounting/finance standards where negative numbers are represented with parenthesis, that is, (200)

If you want your currency to stick with accounting standards where negative numbers are represented with parenthesis, set currencySign to accounting

new Intl.NumberFormat("en-GB", {
  style: "currency",
  currency: "GBP",
}).format(-1001246) // -£1,001,246.00

new Intl.NumberFormat("en-GB", {
  style: "currency",
  currency: "GBP",
  currencySign: "accounting",
}).format(-1001246) // (£1,001,246.00)

Unit

This allows the formatting of unit measurements. This accepts the following options

• unit: It is required if the style is unit, and it refers to units like gram or liter. Full list of the available units can be found here
• unitDisplay: Determine how the units would be written, the default value is short

new Intl.NumberFormat("en-GB", {
  style: "unit",
  unit: "kilometer",
}).format(1001246) //1,001,246 km


new Intl.NumberFormat("en-GB", {
  style: "unit",
  unit: "kilometer",
  unitDisplay: "short",
}).format(1001246) // 1,001,246 km


new Intl.NumberFormat("en-GB", {
  style: "unit",
  unit: "kilometer",
  unitDisplay: "long",
}).format(1001246) // 1,001,246 kilometres


new Intl.NumberFormat("en-GB", {
  style: "unit",
  unit: "kilometer",
  unitDisplay: "narrow",
}).format(1001246) // 1,001,246km

Percent

It will return percentage (%) based on the provided value. It basically multiplies the value provided by 100 and returns it as a percent, so 1 will be 100%.

new Intl.NumberFormat("en-GB", {
  style: "percent",
}).format(1) // 100%


new Intl.NumberFormat("en-GB", {
  style: "percent",
}).format(0.35) // 35%


new Intl.NumberFormat("en-GB", {
  style: "percent",
}).format(35) // 3,500%

Browser Support

Intl.NumberFormat is well-supported in modern web browsers, including Chrome, Firefox, Safari, and Edge. However, if you need to support older browsers, consider using a polyfill like intl-numberformat to ensure consistent behavior.

Conclusion

Intl.NumberFormat is an invaluable tool for formatting numbers in web applications. It allows you to present numeric data in a way that is not only culturally sensitive but also customizable to meet your application's specific needs. By mastering Intl.NumberFormat, you can provide a more user-friendly and globally accessible experience, making your web application more inclusive and appealing to users from around the world.