I have an array with over 50 entries in the form of objects, which I would like to save depending on the Item ID so that I can then apply certain calculations to them. For example, I would like to add up the time of all entries with the Item Id "Las5241Wz".

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Since the array can change dynamically, I can’t analyze it manually. How can I separate the data beforehand according to their Item ID and push them into new arrays? The real Array contains up to 16 objects with the same ID.

var data= []
data = [
  //...objects
{
    itemId: "Las5241Wz", 
    time: 10
  },
  {
    itemId:"Bos1239Zf", 
    time: 11
  },
  {
    itemId:"Las5241Wz", 
    time: 15
  },
  {
    itemId:"Bos1239Zf", 
    time: 21
  }
//...more objets
   ]

The solution for this should look like this:

var Item1 = [
{
    itemId: "Las5241Wz", 
    time: 10
  },
{
    itemId:"Las5241Wz", 
    time: 15
  },
]

var Item2 = [
{
    itemId:"Bos1239Zf", 
    time: 11
  },
{
    itemId:"Bos1239Zf", 
    time: 21
  }
]

>Solution :

Unless you have a performance reason to keep the lists separately, the answer is that you can just store the list of ids as a Set and use array.filter when you want to get the list that is just for that id

Set s = new Set();
for (let i = 0; i < data.length; i++) {
  s.add(data[i].itemId);
}

var createFilterFunc(id) {
  return function(elem) {
    return elem.itemId == id;
  }
}

var items = data.filter (createFilterFunc("Las5241Wz"));