Separador de miles en javascript

separador_miles.js

function format(separator, period) {
  var separator_break = this.toString().split(',');
  var numeric = separator_break[0];
  var decimal = separator_break.length > 1 ? period + separator_break[1] : '';
  var reg = /(\d+)(\d{3})/;
  while (reg.test(numeric)) {
    numeric = numeric.replace(reg, '$1' + separator + '$2');
  }
  return numeric + decimal;
}

$(document).ready(function(){
	$(this).on('keyup','#myinput', function(){
    	$(this).val(format.call($(this).val().split('.').join(''),'.',','));
    });
});