Javascript sort array by "groups" and maintain order - Stack Overflow

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I have a dataset that looks like this:

[
{
    "name": "Item1",
    "section": "section1",
    "total": 3,
}, {
    "name": "Item1",
    "section": "section2",
    "total": 4,
}{
    "name": "Item1",
    "section": "section3",
    "total": 7,
}, {
    "name": "Item2",
    "section": "section1",
    "total": 1,
}, {
    "name": "Item2",
    "section": "section2",
    "total": 2,
}, {
    "name": "Item2",
    "section": "section3",
    "total": 3,
    }
]

I need to sort the array by only the total value in the section 3 item, but maintain the order (section1, section2, then section 3) per name. So for this example Item2 should move all 3 of it's rows above Item1. I've tried sorting by multiple items, but that doesn't maintain the ordering that I need. Should I just get the smallest/biggest, grab the related items and put them into a new array and repeat or is there a more logical way to acplish this?

I'm also using angular and primeng grid if there's something I can leverage in there.

I have a dataset that looks like this:

[
{
    "name": "Item1",
    "section": "section1",
    "total": 3,
}, {
    "name": "Item1",
    "section": "section2",
    "total": 4,
}{
    "name": "Item1",
    "section": "section3",
    "total": 7,
}, {
    "name": "Item2",
    "section": "section1",
    "total": 1,
}, {
    "name": "Item2",
    "section": "section2",
    "total": 2,
}, {
    "name": "Item2",
    "section": "section3",
    "total": 3,
    }
]

I need to sort the array by only the total value in the section 3 item, but maintain the order (section1, section2, then section 3) per name. So for this example Item2 should move all 3 of it's rows above Item1. I've tried sorting by multiple items, but that doesn't maintain the ordering that I need. Should I just get the smallest/biggest, grab the related items and put them into a new array and repeat or is there a more logical way to acplish this?

I'm also using angular and primeng grid if there's something I can leverage in there.

• javascript
• arrays
• angular
• sorting

Share Improve this question Follow asked Mar 31, 2020 at 13:09 ShawnShawn 2,36666 gold badges4949 silver badges8282 bronze badges 3

• you need a stable sort, the build in is not stable IIRC. – apple apple Commented Mar 31, 2020 at 13:12
• what you mean by I've tried sorting by multiple items,? this doesn't sound right to me. – apple apple Commented Mar 31, 2020 at 13:13
• do you have always three items in a group? please add the wanted result. – Nina Scholz Commented Mar 31, 2020 at 13:53

Add a ment  | 

5 Answers 5

Sorted by: Reset to default 3

I would create a map using the name as the key and the total as the value for items where section equals section3. You can then sort using the map.

This will sort all items by the value of the total in section3, and preserve the original sort order where the sort value matches.

const map = new Map<string, number>(this.data
  .filter(x => x.section === 'section3')
  .map(x => [ x.name, x.total ]));

this.sorted = this.data.slice()
  .sort((a, b) => map.get(a.name) - map.get(b.name));

This does rely on the data being structured and ordered as your have specified in your question.

DEMO: https://stackblitz./edit/angular-fsswdq

Priority sort

const data = [{"name":"Item1","section":"section1","total":3},{"name":"Item1","section":"section2","total":4},{"name":"Item1","section":"section3","total":7},{"name":"Item2","section":"section1","total":1},{"name":"Item2","section":"section2","total":2},{"name":"Item2","section":"section3","total":3}];
console.log(
  data.sort((a, b) => {
    const diff = a.total - b.total;
    if (diff) return diff;
    return b.section.localeCompare(a.section);
  })
);

.as-console-row {color: blue!important}

You could

• collect all object of the same group and get the total for sorting,
• sort by the groups total value,
• get a flat array of all objects.

const
    data = [{ name: "Item1", section: "section1", total: 3 }, { name: "Item1", section: "section2", total: 4 }, { name: "Item1", section: "section3", total: 7 }, { name: "Item2", section: "section1", total: 1 }, { name: "Item2", section: "section2", total: 2 }, { name: "Item2", section: "section3", total: 3 }],
    result = Object
        .values(data.reduce((r, o) => {
            r[o.name] = r[o.name] || { payload: [] };
            r[o.name].payload.push(o);
            if (o.section === 'section3') r[o.name].total = o.total;
            return r;
        }, {}))
        .sort(({ total: a }, { total: b }) => a - b)
        .flatMap(({ payload }) => payload);

console.log(result);

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

var array = [
{
    "name": "Item1",
    "section": "section1",
    "total": 3,
}, {
    "name": "Item1",
    "section": "section2",
    "total": 4,
},{
    "name": "Item1",
    "section": "section3",
    "total": 7,
}, {
    "name": "Item2",
    "section": "section1",
    "total": 1,
}, {
    "name": "Item2",
    "section": "section2",
    "total": 2,
}, {
    "name": "Item2",
    "section": "section3",
    "total": 3,
    }
];

array = array.sort((o1, o2)=>{

if(o1.section === o2.section && o1.section === 'section3') {
   return o1.total - o2.total;
} else {
  return o1.section === 'section3' ? 1 : -1;
}
});

console.log(array);

Here's the output

[
  {
    "name": "Item1",
    "section": "section1",
    "total": 3
  },
  {
    "name": "Item1",
    "section": "section2",
    "total": 4
  },
  {
    "name": "Item2",
    "section": "section1",
    "total": 1
  },
  {
    "name": "Item2",
    "section": "section2",
    "total": 2
  },
  {
    "name": "Item2",
    "section": "section3",
    "total": 3
  },
  {
    "name": "Item1",
    "section": "section3",
    "total": 7
  }
]

You first need to "Group" the data set by name and then do the sorting by total.

let items = [{
  "name": "Item1",
  "section": "section1",
  "total": 3,
}, {
  "name": "Item1",
  "section": "section2",
  "total": 4,
}, {
  "name": "Item1",
  "section": "section3",
  "total": 7,
}, {
  "name": "Item2",
  "section": "section1",
  "total": 1,
}, {
  "name": "Item2",
  "section": "section2",
  "total": 2,
}, {
  "name": "Item2",
  "section": "section3",
  "total": 3,
}];

let groups = {};

for (let item of items) {
  if (!groups[item.name]) {
    groups[item.name] = {
      data: []
    };
  }

  // Grouping by `name`
  groups[item.name].data.push(item);

  // Store the `total`
  if (item.section == "section3") {
    groups[item.name].key = item.total;
  }
}

// sort the groups, this will maintain the order of sections (1,2 and 3) in each group
let sortedGroups = Object.values(groups).sort((a, b) => {
  return a.key - b.key; // ascending
});

// then flatten the groups
let flatten = [].concat(...sortedGroups.map(x => x.data));

console.log(flatten);

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