function json() {
  vToArr();
  var str = JSON.stringify(json_training);
  myJSON = str;
}

function vToArr(){
  for(var a = 0; a <= x; a++){
    json_training[y] = {};
    var arrExercise = document.getElementsByClassName('exercise')[counter].value;
    if(arrExercise != ""){json_training[y]["uebung"] = arrExercise;}else{json_training[y]["uebung"] = "-";};
    var arrDevice = document.getElementsByClassName('device')[counter].value;
    if(arrDevice != "hidden"){json_training[y]["geraet"] = arrDevice;}else{json_training[y]["geraet"] = "-";}
    var arrWeigth = document.getElementsByClassName('weigthValue')[counter].value;
    json_training[y]["gewicht"] = arrWeigth;
    var arrRepeat = document.getElementsByClassName('repeatsValue')[counter].value;
    json_training[y]["wiederholungen"] = arrRepeat;
    y++;
    counter = [y];
  }
  y = 0;
  counter = [0];
}