Recipe 11.8

Applying Pluralization Rules

Intl.PluralRules can tell you what form of a message string you should use based on the number passed to its select method.

It returns a key such as one or other (differs depending on the locale) that you can use to look up different messages.

Code

JavaScript

function formatUserCount(users) {
  // The variations of the message, depending
  // on the count.
  const messages = {
    one: 'There is 1 user.',
    other: `There are ${users.length} users.`
  };

  // Use Intl.PluralRules to determine which message
  // should be displayed.
  const rules = new Intl.PluralRules('en-US');
  return messages[rules.select(users.length)];
}