function charsLeftIndex(string, chars) {
    var index = -1,
        length = string.length;

    while (++index < length) {
      if (chars.indexOf(string.charAt(index)) < 0) {
        break;
      }
    }
    return index;
  }
Gets the index of the first character of `string` that is not found in `chars`.

@private
@param {string} string The string to inspect.
@returns {number} Returns the index of the first character not found in `chars`.