How do I iterate over a JSON structure?

var arr = [ {"id":"10", "class": "child-of-9"}, {"id":"11", "class": "child-of-10"}];

    

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

  document.write("<br><br>array index: " + i);

  var obj = arr[i];

  for (var key in obj){

    var value = obj[key];

    document.write("<br> - " + key + ": " + value);

  }

}

var mycars = [{name:'Susita'}, {name:'BMW'}];



for (var car of mycars) 

{

  document.write(car.name + "<br />");

}