JavaScript: Locale

Locale is specified as a string. Normally

language (2 char, lower case) “-” Country (2 char, upper case)

but can also include a script (latn (Latin), cyrl (Cyrillic), hans (simplified chinese) and variants and extensions.

Numbers

let myNumber = 12345.67
console.log(myNumber.toLocaleString(“en-GB”));  // → 12,345.67
console.log(myNumber.toLocaleString(“de-DE”));  // → 12.345,67

Also number formatter

let formatter = new Intl.NumberFormat(“de”);
formatter.format(12345.67);

You can add options

let formatter = new Intl.NumberFormat(“de”, {style:”currency”, currency:”EUR”});
formatter.format(12345.67);  → 12.345,67 €

Options include

  • styles: decimal (default), currency, percent
  • currency: ISO4217 code
  • currencyDisplay: symbol (default), code, name
  • minimumIntegerDigits, minimumFractionDigits, maximumFractionDigits, minimumSignificantDigits, maximumSignificantDigits,

Dates

let myDate = new Date();
console.log(myDate.toLocaleString(“en”));  //→ 5/17/2022, 8:41:38 PM
console.log(myDate.toLocaleDateString(“en-GB”));  // → 17/05/2022
console.log(myDate.toLocaleTimeString(“en”)); // → 8:41:38 PM

Note “en” defaults to “en-US”.

Also date formatter

let formatter = new Intl.DateTimeFormat(“en”);
formatter.format(myDate);

Can add options

let formatter = new Intl.DateTimeFormat(“en”, {});
formatter.format(myDate);

Options include

  • timezone: UTC, Europe/London, Europe/Paris
  • dateStyle, timeStyle: full, long, medium, short
  • month: 2-digit, numeric, narrow, short, long
  • year, day, hour, minute, second: 2-digit, numeric
  • weekday, era: short, long, narrow
  • timeZoneName: short, long

Other functions include generating text for a “relative time”.

let formatter = new Intl.RelativeTimeFormat(“en”, {});
console.log(formatter.format(3, “hours”); //→ in 3 hours

Sorting & Collation

When sorting an array, there was the comparator function

myArray.sort( (x,y) => x.localeCompare(y) )

Can also use a collator for localised collation.

const swedishCollator = new Intl.Collator(“sv”);
myArray.sort(swedishCollator.compare)