(?:^(?:[0-9]{1,3})(?:(?:\.{0,1}(?:[0-9]{3}))\b)+)$|(^[0-9]+$)
let matches = string.match(/(^\d+|^\-\d+)/gi);
string.replace(/\d(?=(\d{3})+\.)/g, '$&,');
return /^-?[0-9]+(\.\d+)?$/g.test(string);
(?:^(?:[0-9]{1,3})(?:(?:\.{0,1}(?:[0-9]{3}))\b)+)$|(^[0-9]+$)
let matches = string.match(/(^\d+|^\-\d+)/gi);
string.replace(/\d(?=(\d{3})+\.)/g, '$&,');
return /^-?[0-9]+(\.\d+)?$/g.test(string);