Count repeated letters in a string

Question

I\'m stuck with the following problem: I need to find repeated characters in a string. Basically what I want is regular expression that will match like that

Answer 1

var re = /([a-z])(?:.*)(\1)+/g; 
var str = ['aaaccbcdd'];
var m;
var result = new Array();

for(var i = 0; i < str.length; i++) {
  result[i] = str[i] + "->";
  while ((m = re.exec(str[i])) !== null) {
      if (m.index === re.lastIndex) {
          re.lastIndex++;
      }
      // View your result using the m-variable.
      // eg m[0] etc.
    result[i] += m[1];
    result[i] += m[2] + ",";
  }
}

document.getElementById("results").innerHTML = result.join("
");