Javascript | Grouping objects

Question

I have an object. It looks like this:

[
  {
    "name":"Display",
    "group":"Technical detals",
    "id":"60",
    "value":"4"
  },
  {
    "name":"Manufacturer",
    "group":"Manufacturer",
    "id":"58",
    "value":"Apple"
  },
  {
    "name":"OS",
    "group":"Technical detals",
    "id":"37",
    "value":"Apple iOS"
  }
]

I would like to group this data by group field and get this object:

var obj = {
    0 = [
    {
       'group'   = 'Technical detals',
       'name'    = 'Display',
       'id'      = '60',
       'value'   = '4'
    },
    {
       'group'   = 'Technical detals',
       'name'    = 'OS',
       'id'      = '37',
       'value'   = 'Apple iOS'
    }],
    1   = [
    {
       'group'   = 'Manufacturer',
       'name'    = 'Manufacturer',
       'id'      = '58',
       'value'   = 'Apple'
    }]
}

How can I group my first object?

Answer 1

Try something like this:

function groupBy(collection, property) {
    var i = 0, val, index,
        values = [], result = [];
    for (; i < collection.length; i++) {
        val = collection[i][property];
        index = values.indexOf(val);
        if (index > -1)
            result[index].push(collection[i]);
        else {
            values.push(val);
            result.push([collection[i]]);
        }
    }
    return result;
}

var obj = groupBy(list, "group");

Keep in mind that it is Array.prototype.indexOfnot defined in IE8 and later, but there are common policies for this.

Answer 2

If you use underscore.js in your application, you can simply do the following:

var groups = _.groupBy(data, 'group'); // data is your initial collection

Or, if you prefer not to use any library, you can do it yourself:

var groups = { };
data.forEach(function(item){
   var list = groups[item.group];

   if(list){
       list.push(item);
   } else{
      groups[item.group] = [item];
   }
});

http://jsfiddle.net/nkVu6/3/

Answer 3

- Array#forEach .

, , , .

.

function groupBy(array, group) {
    var hash = Object.create(null),
        result = [];

    array.forEach(function (a) {
        if (!hash[a[group]]) {
            hash[a[group]] = [];
            result.push(hash[a[group]]);
        }
        hash[a[group]].push(a);
    });
    return result;
}

var data = [{ name: "Display", group: "Technical detals", id: 60, value: 4 }, { name: "Manufacturer", group: "Manufacturer", id: 58, value: "Apple" }, { name: "OS", group: "Technical detals", id: 37, value: "Apple iOS" }];
	
console.log(groupBy(data, "group"));

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Answer 4

ES6 Map, :

function groupBy(arr, prop) {
    const map = new Map(Array.from(arr, obj => [obj[prop], []]));
    arr.forEach(obj => map.get(obj[prop]).push(obj));
    return Array.from(map.values());
}

const data = [{ name: "Display", group: "Technical detals", id: 60, value: 4 }, { name: "Manufacturer", group: "Manufacturer", id: 58, value: "Apple" }, { name: "OS", group: "Technical detals", id: 37, value: "Apple iOS" }];
	
console.log(groupBy(data, "group"));

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Map /, . , .

. , (.. ).

Answer 5

Reduce . list :

const list = [{
    'name': 'Display',
    'group': 'Technical detals',
    'id': '60',
    'value': '4'
  },
  {
    'name': 'Manufacturer',
    'group': 'Manufacturer',
    'id': '58',
    'value': 'Apple'
  },
  {
    'name': 'OS',
    'group': 'Technical detals',
    'id': '37',
    'value': 'Apple iOS'
  }
];

const groups = list.reduce((groups, item) => {
  const group = (groups[item.group] || []);
  group.push(item);
  groups[item.group] = group;
  return groups;
}, {});

console.log(groups);

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, reduce :

const list = [{
    'name': 'Display',
    'group': 'Technical detals',
    'id': '60',
    'value': '4'
  },
  {
    'name': 'Manufacturer',
    'group': 'Manufacturer',
    'id': '58',
    'value': 'Apple'
  },
  {
    'name': 'OS',
    'group': 'Technical detals',
    'id': '37',
    'value': 'Apple iOS'
  }
];

const groups = list.reduce((groups, item) => ({
  ...groups,
  [item.group]: [...(groups[item.group] || []), item]
}), {});

console.log(groups);

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, .

Answer 6

lodash, groupBy.

, .

:

_.groupBy([6.1, 4.2, 6.3], Math.floor);
// => { '4': [4.2], '6': [6.1, 6.3] }

// The `_.property` iteratee shorthand.
_.groupBy(['one', 'two', 'three'], 'length');
// => { '3': ['one', 'two'], '5': ['three'] }

Answer 7

I tried to use the answer marked as accepted, but noticed that in some groups there are no elements, depending on the type of property being evaluated. This is a solution derived from this answer:

function groupBy(collection, property) {
  var i = 0, values = [], result = [];
  for (i; i < collection.length; i++) {
    if(values.indexOf(collection[i][property]) === -1) {
      values.push(collection[i][property]);
      result.push(collection.filter(function(v) { return v[property] === collection[i][property] }));
    }
  }
  return result;
}
var obj = groupBy(list, "group");

Answer 8

Try

let g = (d,h={},r={},i=0)=>(d.map(x=>(y=x.group,h[y]?1:(h[y]=++i,r[h[y]-1]=[]),r[h[y]-1].push(x))),r);
console.log( g(data) );

let data=[
  {
    "name":"Display",
    "group":"Technical detals",
    "id":"60",
    "value":"4"
  },
  {
    "name":"Manufacturer",
    "group":"Manufacturer",
    "id":"58",
    "value":"Apple"
  },
  {
    "name":"OS",
    "group":"Technical detals",
    "id":"37",
    "value":"Apple iOS"
  }
];


let g = (d,h={},r={},i=0)=>(d.map(x=>(y=x.group,h[y]?1:(h[y]=++i,r[h[y]-1]=[]),r[h[y]-1].push(x))),r);

console.log(g(data));

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