Javascript sort array by "groups" and maintain order

Question

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 accomplish this?

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

what you mean by I've tried sorting by multiple items,? this doesn't sound right to me. — apple apple
– 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
– Nina Scholz, Commented Mar 31, 2020 at 13:53

Kurt Hamilton · Accepted Answer · 2020-03-31 13:17:39Z

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.com/edit/angular-fsswdq

answered Mar 31, 2020 at 13:17

Kurt Hamilton

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Comments

xdeepakv · Accepted Answer · 2020-03-31 13:47:33Z

2

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}

edited Mar 31, 2020 at 13:47

answered Mar 31, 2020 at 13:34

xdeepakv

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Comments

Nina Scholz · Accepted Answer · 2020-03-31 14:04:14Z

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; }

Tanmay_vijay · Accepted Answer · 2020-03-31 13:20:10Z

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
  }
]

Rick Su · Accepted Answer · 2020-03-31 13:29:09Z

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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