JavaScript Intl.NumberFormat - Format Numbers Without Libraries

Problem

Installing numeral.js or accounting.js just to display “1,000” or “$1,234.56”. There’s a built-in browser API that handles this already.

Solution

// Korean Won
new Intl.NumberFormat('ko-KR', {
  style: 'currency',
  currency: 'KRW',
  minimumFractionDigits: 0,
}).format(15000);
// → "₩15,000"

// Thousands separator
new Intl.NumberFormat('ko-KR').format(1234567);
// → "1,234,567"

// US Dollar
new Intl.NumberFormat('en-US', {
  style: 'currency',
  currency: 'USD',
}).format(1234.5);
// → "$1,234.50"

// Percentage
new Intl.NumberFormat('ko-KR', {
  style: 'percent',
  minimumFractionDigits: 1,
}).format(0.1234);
// → "12.3%"

Key Points

• Intl.NumberFormat is supported in all modern browsers and Node.js. Even IE11 handles the basics.
• currency: 'KRW' displays without decimals, while 'USD' automatically adds 2 decimal places. Each currency follows its own conventions.
• For repeated use, store the formatter instance in a variable. Creating new instances every time is wasteful.