Mask String with Thousand Separator

index.js

/**
 * Masks Input with thousand separator
 *
 * @param {string} amount - Amount
 * @return {string} Masked Amount
 *
 * @example
 * formatAmount("1000") // 1,000
 */
export function formatAmount(amount) {
  if (!amount) return;
  return amount
    .toString()
    .replace(/,/g, "")
    .replace(/\B(?=(\d{3})+(?!\d))/g, ",");
}

/**
 * Normalizes Amount from Masked format
 *
 * @param {string} amount - Amount
 * @return {string} Normalized Amount
 *
 * @example
 * normalizeAmount("1,000") // 1000
 */
export function normalizeAmount(amount) {
  return amount.toString().replace(/,/g, "");
}