Returning null value in dictionary of JSON

user10593822

Write a function named "json_average" that takes a JSON formatted string as a parameter in the format of an array of objects where each object has keys "mass", "density", "temperature", and "velocity" and each key maps to a floating point number. This function should return the average "velocity" of all the objects in the array as a JSON string in the format {"velocity": }

function json_average(JSON1){
    var load = JSON.parse(JSON1);
    var sum = 0;
    var sum1 = 0;
    var dictionary = {};
    for (var i in load){
        sum += i.velocity;
        sum1 += 1;
    }
    var average = sum / sum1;
    dictionary.velocity = average;
    return JSON.stringify(dictionary);
}

console.log(json_average('[{"velocity": 1}, {"velocity": 10}]'));

I keep returning the value of 'velocity' as null. What am I doing wrong?

slider

Because it's an array, you want to use for i of load:

function json_average(JSON1) {
  var load = JSON.parse(JSON1);
  var sum = 0;
  var sum1 = 0;
  var dictionary = {};
  for (var i of load) {
    sum += i.velocity;
    sum1 += 1;
  }
  var average = sum / sum1;
  dictionary.velocity = average;
  return JSON.stringify(dictionary);
}

console.log(json_average('[{"velocity": 1}, {"velocity": 10}]'));

for...in is used to iterate over keys of an object.

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