format-inbox-count.ts324 BView on GitHub
const compactCountFormatter = new Intl.NumberFormat('en', {
  notation: 'compact',
  maximumFractionDigits: 1,
});

export function formatInboxCount(count: number, isExact: boolean): string {
  const display = count < 1000 ? String(count) : compactCountFormatter.format(count);
  return isExact ? display : `${display}+`;
}