统计字符串里出现出现频率最多的字符

function getMostFreq(str) {
  var dict = {};
  var max = 0;
  var maxCh;
  for (var i = 0; i < str.length; i++) {
    var ch = str[i];
    if (dict[ch] === undefined) {
      dict[ch] = 1;
    } else {
      dict[ch]++;
    }
    if (dict[ch] > max) {
      max = dict[ch];
      maxCh = str[i];
    }
  }
  return { index: max, ch: maxCh };
}

var str = 'hjhghhhhooowoldhh';
console.log(getMostFreq(str)); //  { index: 8, ch: 'h' }