I am receiving undefined when using charAt[i]

I am not sure why I am receiving undefined when I loop through data which is a string, To see if data contained a string I did console.log(typeof data + ": " + data); which echoed out String : 26.19. From my understanding, I thought looping through the data string and using charAt[i] I should in theory return the character at i, however, I am receiving undefined. Why is that and how do I return the character at i?

s7s.prototype.sendValue = function (data) {
  var a = this.address;
  var length = data.length;
  var i;
  var val;
  var dpLoc;

  console.log(typeof data + ": " + data); //echos out a string

  for(i=0; i<data.length; i++) {
    var char = data.charAt[i];

    console.log(data.charAt[i]);

    if(char != ".") {
      val += char;
    }

    if(char == ".") {
      dpLoc = i;
    }
  }

  //console.log(val);

  //I2C2.writeTo(a, value);
};