// an array of random years
var years = [1990, 1965, 1937, 1998, 1988];

// function to place all given values into a new array in this case arrRes
function arrayCalc(arr, fn){
  var arrRes = [];
  for (var i = 0; i < arr.length; i++) {
    arrRes.push(fn(arr[i]));
  }
  return arrRes;
}


//function to calculate the age
function calcage(el){
  return  2019 - el;
}


var ages = arrayCalc(years, calcage);
console.log(ages);