I'm working on a codecademy.com lesson with instructions to write the calculateTotal function below. When I click run, it's returning NaN. Anyone know what's wrong with the calculateTotal function as I wrote it that's making it return NaN. Note, I understand that NaN means not a number...

// runner times

var carlos = [9.6,10.6,11.2,10.3,11.5];

var liu = [10.6,11.2,9.4,12.3,10.1];

var timothy = [12.2,11.8,12.5,10.9,11.1];



// declare your function calculateTotal here

var calculateTotal = function(raceTimes){

    var totalTime; 

    for(i = 0; i < raceTimes.length; i++){

        totalTime += raceTimes[i]; 

        return totalTime; 

    }

};



var liuTotal = calculateTotal(liu);



console.log(liuTotal);

Note, many of the people answering this question have said that var totalTime has to be set to O. However, in the next codecademy lessson, the author writes a function with totalTime not set to anything and it works

var calculateAverage = function (raceTimes) {

  var totalTime;

  for ( i = 0; i < raceTimes.length; i++ ) {

    totalTime = (totalTime || 0) + raceTimes[i];

  }

// assign variable averageTime

var averageTime = totalTime / raceTimes.length; 



  return averageTime;

};