function removeDubCharacters (str) {
  var reg = /(.)\1{2,}/g;
  if(str.match(reg)) {
    str = str.replace(reg, '$1$1');
  }
  return str;
}

function removeDubCharacters (str) {
  var reg = /(.)\1{2,}/;
  if(str.match(reg)) {
    str = str.replace(reg, '$1$1');
  }
  return str;
}

function removeDubCharacters (str) {
  var reg = /(.)\1{2,}/;
  if(str.match(reg)) {
    str = str.replace(reg, '$1$1');
  }
}

function removeDubCharacters (elem) {
  var reg = /(\w)\1+\1+/g;
  if(elem.match(reg)) {
    elem = elem.replace(reg, '$1$1');
  }
}

This function removes repeated characters after second one

Remove Duplicate Characters

JavaScript