Javascript - Find the highest number with same key from a multi dimensional array

Mathieu
September 30, 2023
193 views
2 votes
3 Answers

I have this array :

data = {
  "lists": {
    "list-1": {
      "id": "list-1",
      "title": "list1",
      "cards": [
        {
          "id": "20",
          "title": "title"
        },
        {
          "id": "2",
          "title": "title"
        }
      ]
    },
    "list-2": {
      "id": "list-2",
      "title": "list2",
      "cards": [
        {
          "id": "4",
          "title": "title"
        },
        {
          "id": "3",
          "title": "title"
        }
      ]
    }
  }
}

I want to find the highest item with "id" as key. So here it would be "20"

I know how to do within an array but not from a multi dimensional array like here

const list = data.lists[listId]

Answers

const entryWithHighestID = 
  Object.entries(data.lists)          // from all the entries of data.lists
    .map(([key, { cards }]) => cards) // extract the cards property
    .flat()                           // flat to a single array
    .sort((a, b) => b.id - a.id)[0];  // sort by id descending, and get the first entry

Reduce the lists to a min value of card ids:

const max = Object.keys(data.lists).reduce((r, key) => data.lists[key].cards.forEach(card => +card.id > r.id && (r = card)) || r, {id: -1});
console.log(max);

<script>
const data={lists:{"list-1":{id:"list-1",title:"list1",cards:[{id:"20",title:"title"},{id:"2",title:"title"}]},"list-2":{id:"list-2",title:"list2",cards:[{id:"4",title:"title"},{id:"3",title:"title"}]}}};
</script>

If you want the maximum speed, just loop:

let max = {id: -1};

for(const key in data.lists){
  const cards = data.lists[key].cards;
  for(let i = 0; i < cards.length; i++){
    const card = cards[i];
    if(+card.id > max.id) max = card;
  }
}
console.log(max);

<script>
const data={lists:{"list-1":{id:"list-1",title:"list1",cards:[{id:"20",title:"title"},{id:"2",title:"title"}]},"list-2":{id:"list-2",title:"list2",cards:[{id:"4",title:"title"},{id:"3",title:"title"}]}}};
</script>

` Chrome/117
----------------------------------------------------------------------------
Alexander fast looping           1.0x  |  x10000000  334  343  344  345  358
pilchard's tweak to one-liner    1.2x  |  x10000000  397  400  405  407  410
Alexander one-liner              1.3x  |  x10000000  424  427  429  429  432
moonwave99                      15.3x  |   x1000000  512  512  513  519  521
----------------------------------------------------------------------------
https://github.com/silentmantra/benchmark `

const data={lists:{"list-1":{id:"list-1",title:"list1",cards:[{id:"20",title:"title"},{id:"2",title:"title"}]},"list-2":{id:"list-2",title:"list2",cards:[{id:"4",title:"title"},{id:"3",title:"title"}]}}};

// @benchmark moonwave99
Object.entries(data.lists)         // from all the entries of data.lists
    .map(([key, { cards }]) => cards) // extract the cards property
    .flat()                           // flat to a single array
    .sort((a, b) => b.id - a.id)[0];

// @benchmark pilchard's tweak to one-liner
Object.keys(data.lists).reduce((r, key) => data.lists[key].cards.reduce((c, card) => +card.id > c.id ? card : c, r), {id: -1});

// @benchmark Alexander one-liner
Object.keys(data.lists).reduce((r, key) => data.lists[key].cards.forEach(card => +card.id > r.id && (r = card)) || r, {id: -1});

// @benchmark Alexander fast looping
let max = {id: -1};

for(const key in data.lists){
  const cards = data.lists[key].cards;
  for(let i = 0; i < cards.length; i++){
    const card = cards[i];
    if(+card.id > max.id) max = card;
  }
}
max;

/*@end*/eval(atob('e2xldCBlPWRvY3VtZW50LmJvZHkucXVlcnlTZWxlY3Rvcigic2NyaXB0Iik7aWYoIWUubWF0Y2hlcygiW2JlbmNobWFya10iKSl7bGV0IHQ9ZG9jdW1lbnQuY3JlYXRlRWxlbWVudCgic2NyaXB0Iik7dC5zcmM9Imh0dHBzOi8vY2RuLmpzZGVsaXZyLm5ldC9naC9zaWxlbnRtYW50cmEvYmVuY2htYXJrL2xvYWRlci5qcyIsdC5kZWZlcj0hMCxkb2N1bWVudC5oZWFkLmFwcGVuZENoaWxkKHQpfX0='));

You can find the highest item with the "id" key from the given multidimensional array by iterating through the nested structures and keeping track of the highest value found. Here’s a JavaScript function that accomplishes this:

Most Efficient method: 120OP/s

const data = {
  "lists": {
    "list-1": {
      "id": "list-1",
      "title": "list1",
      "cards": [
        {
          "id": "20",
          "title": "title"
        },
        {
          "id": "2",
          "title": "title"
        }
      ]
    },
    "list-2": {
      "id": "list-2",
      "title": "list2",
      "cards": [
        {
          "id": "4",
          "title": "title"
        },
        {
          "id": "3",
          "title": "title"
        }
      ]
    }
  }
};
function findHighestId(data) {
  let highestId = -1;

  for (const listKey in data.lists) {
    const list = data.lists[listKey];

    for (const card of list.cards) {
      const cardId = parseInt(card.id, 10);

      if (!isNaN(cardId) && cardId > highestId) {
        highestId = cardId;
      }
    }
  }

  return highestId;
}

const highestId = findHighestId(data);
console.log("Highest ID:", highestId); // Output: Highest ID: 20

Another way to write it: 86K OP/s

const data = {
  "lists": {
    "list-1": {
      "id": "list-1",
      "title": "list1",
      "cards": [
        {
          "id": "20",
          "title": "title"
        },
        {
          "id": "2",
          "title": "title"
        }
      ]
    },
    "list-2": {
      "id": "list-2",
      "title": "list2",
      "cards": [
        {
          "id": "4",
          "title": "title"
        },
        {
          "id": "3",
          "title": "title"
        }
      ]
    }
  }
};

function findHighestId(data) {
  return Object.values(data.lists)
    .flatMap(list => list.cards)
    .map(card => parseInt(card.id))
    .filter(id => !isNaN(id))
    .reduce((highestId, currentId) => Math.max(highestId, currentId), -1);
}

const highestId = findHighestId(data);
console.log("Highest ID:", highestId); // Output: Highest ID: 20

One last attempt… this can be done many ways: 86K OP/s

const data = {
  "lists": {
    "list-1": {
      "id": "list-1",
      "title": "list1",
      "cards": [
        {
          "id": "20",
          "title": "title"
        },
        {
          "id": "2",
          "title": "title"
        }
      ]
    },
    "list-2": {
      "id": "list-2",
      "title": "list2",
      "cards": [
        {
          "id": "4",
          "title": "title"
        },
        {
          "id": "3",
          "title": "title"
        }
      ]
    }
  }
};


const highestId = Object.values(data.lists)
  .flatMap(list => list.cards)
  .reduce((highest, card) => {
    const cardId = parseInt(card.id);
    return cardId > highest ? cardId : highest;
  }, -1);

console.log("Highest ID:", highestId);

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Javascript – Find the highest number with same key from a multi dimensional array

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