What is the proper way to arrange this particular array?

Question

What is the proper way to arrange this particular array?

I'm having trouble with sorting this array. The array contains objects with SortTime and Operation values like this:

array = [ {SortTime : 123456, Operation : Assigning}, {SortTime : 4567 , Operation: Assigning}, {SortTime : 123456 , Operation: Assigned} ];

When comparing array[0] and array[2], I want to maintain the order so that "Assigning" comes before "Assigned".

Each of these numbers is an epoch number, so I need the algorithm to preserve the original order if two numbers are equal (e.g., if array[4] = 12345 and array[5] = 12345, I don't want them to switch positions in the final order).

    array.sort(function(a, b) {
        if (a.val.SortTime === b.val.SortTime) {
            return -1;
        } else {
            return a.val.SortTime - b.val.SortTime;
        }
    });

This approach isn't working because it often swaps positions of equal numbers. I apologize if my explanation is unclear. Thank you for your help!

javascript arrays sorting stable-sort

Answer 1

Answer №1

To maintain the relationship between items with the same time, consider adding an index property to the objects and then sorting based on both time and index.

This approach results in a stable outcome due to the inclusion of the index.

var data = [
        { TimeStamp: 123456, Action: 'Update', index: 0 },
        { TimeStamp: 912345, Action: 'Delete', index: 1 },
        { TimeStamp: 123456, Action: 'Create', index: 2 }
    ]; 

data.sort(function (x, y) {
    return x.TimeStamp - y.TimeStamp || x.index - y.index;
});

console.log(data);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

To maintain the relationship between items with the same time, consider adding an index property to the objects and then sorting based on both time and index.

This approach results in a stable outcome due to the inclusion of the index.

var data = [
        { TimeStamp: 123456, Action: 'Update', index: 0 },
        { TimeStamp: 912345, Action: 'Delete', index: 1 },
        { TimeStamp: 123456, Action: 'Create', index: 2 }
    ]; 

data.sort(function (x, y) {
    return x.TimeStamp - y.TimeStamp || x.index - y.index;
});

console.log(data);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 3

Answer №2

If you're looking for a reliable way to sort, consider using a stable sort algorithm. You can find a variety of options on Wikipedia's list of stable sort algorithms.

For a practical example, here is an implementation of the merge sort algorithm from Rosetta Code available at this link:

function merge(left, right, arr) {
  var a = 0;
 
  while (left.length && right.length) {
    arr[a++] = (right[0] < left[0]) ? right.shift() : left.shift();
  }
  while (left.length) {
    arr[a++] = left.shift();
  }
  while (right.length) {
    arr[a++] = right.shift();
  }
}
 
function mergeSort(arr) {
  var len = arr.length;
 
  if (len === 1) { return; }
 
  var mid = Math.floor(len / 2),
      left = arr.slice(0, mid),
      right = arr.slice(mid);
 
  mergeSort(left);
  mergeSort(right);
  merge(left, right, arr);
}
 
var arr = [1, 5, 2, 7, 3, 9, 4, 6, 8];
console.log(arr);
mergeSort(arr)
console.log(arr);

Answer 4

If you're looking for a reliable way to sort, consider using a stable sort algorithm. You can find a variety of options on Wikipedia's list of stable sort algorithms.

For a practical example, here is an implementation of the merge sort algorithm from Rosetta Code available at this link:

function merge(left, right, arr) {
  var a = 0;
 
  while (left.length && right.length) {
    arr[a++] = (right[0] < left[0]) ? right.shift() : left.shift();
  }
  while (left.length) {
    arr[a++] = left.shift();
  }
  while (right.length) {
    arr[a++] = right.shift();
  }
}
 
function mergeSort(arr) {
  var len = arr.length;
 
  if (len === 1) { return; }
 
  var mid = Math.floor(len / 2),
      left = arr.slice(0, mid),
      right = arr.slice(mid);
 
  mergeSort(left);
  mergeSort(right);
  merge(left, right, arr);
}
 
var arr = [1, 5, 2, 7, 3, 9, 4, 6, 8];
console.log(arr);
mergeSort(arr)
console.log(arr);

Answer 5

Answer №3

To see a live demo, visit JSFiddle

let data = [ 
     { 
       Length: 54321, 
       Task: 'third task'
     }, {
       Length: 8765,
       Task: 'Calculating'
     }, {
       Length: 54321,
       Task: 'fourth task'
     }];

let duplicate = [...data];

duplicate.sort(function(x, y) {
    if (x.val.Length === y.val.Length) {
        return data.indexOf(x) - data.indexOf(y);
    } else {
        return x.val.Length - y.val.Length;
    }
});

Answer 6

To see a live demo, visit JSFiddle

let data = [ 
     { 
       Length: 54321, 
       Task: 'third task'
     }, {
       Length: 8765,
       Task: 'Calculating'
     }, {
       Length: 54321,
       Task: 'fourth task'
     }];

let duplicate = [...data];

duplicate.sort(function(x, y) {
    if (x.val.Length === y.val.Length) {
        return data.indexOf(x) - data.indexOf(y);
    } else {
        return x.val.Length - y.val.Length;
    }
});

What is the proper way to arrange this particular array?

Answer №1

Answer №2

Answer №3

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