Utils to validate and format credit card numbers

pan.js

var validatePAN = function(pan){
  pan = pan.replace(/[^\d]+/g, '');
  if (pan.length < 12)
    return false;

  var even = false;
  var check = 0;
  for (var i = pan.length - 1; i >= 0; i--) {
    var n = pan[i]|0;
    if (even) {
      n *= 2;
      if (n > 9)
        n -= 9;
    }

    check += n;
    even = !even;
  }

  return (check % 10) == 0;
}

var formatPAN = function(input){
  var getCaretPosition = function(input){
    if ('selectionStart' in input) {
      // Standard-compliant browsers
      return input.selectionStart;
    } else if (document.selection) {
      // IE
      input.focus();
      var sel = document.selection.createRange();
      var selLen = document.selection.createRange().text.length;
      sel.moveStart('character', -input.value.length);
      return sel.text.length - selLen;
    }
  }

  var setCaretPosition = function(input, position){
    if ('selectionStart' in input) {
      // Standard-compliant browsers
      input.setSelectionRange(position, position);
    } else {
      // IE
      var range = input.createTextRange();
      range.move('character', position);
      range.select();
    }
  }

  var caretPosition = getCaretPosition(input);
  var caretOffset = 0;
  var pan = input.value;

  var panGroups = [];
  var lastPanGroup = '';

  for (var i = 0; i < pan.length; i++) {
    if (isNaN(parseInt(pan[i]))) {
      if (i < caretPosition) {
        caretOffset--;
      }
    } else {
      lastPanGroup += pan[i];
      if (lastPanGroup.length == 4) {
        panGroups.push(lastPanGroup);
        lastPanGroup = '';
      }
    }
  }

  panGroups.push(lastPanGroup);
  pan = panGroups.join(' ').trim();

  caretOffset += (caretPosition / 5.0)|0;

  input.value = pan;
  setCaretPosition(input, caretPosition + caretOffset);
}