Record Collection Challenge: Value and [Value];

JavaScript
1 
function updateRecords(id, prop, value) {
  if (prop === "tracks" && value !== "") {
   if(collection[id][prop]) {
    collection[id][prop].push(value);
   }
   else {
    collection[id][prop]=[value];
   }
  } else if (value !== "") {
    collection[id][prop] = value;
  } else {
    delete collection[id][prop];
  }

  return collection;
}

Can you please shed some light on the difference between collection[id][prop] = [value] and collection[id][prop] = value ? The problem has haunted me for few days. Thank you loads!
The code above is from Basic Code Solution in guide section. Have a nice day!

3

Thank you for the clarification! Can I have one more question?

Consider this specific piece of code:

else if (value !== "") {
    collection[id][prop] = value;
  }

In the case the property is not "tracks", is this the part that will update or set the value for that property? Or it does both?

Thank you again for the explanation. Have a nice day!