isLetter Number check js code example

Example 1: number with commas js

function numberWithCommas(x) {
  return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ',');
}

Example 2: just number regex js

// https://regex101.com/r/qyq3PG/1
// or 
/^[0-9]*$/