javascript | Object grouping

Question

I have an object. It looks like below:

[
  {
    "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

Reduce is great for situations like this. Given list below is your input data:

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);

And if you wanted to be immutable, you could write the reduce like this:

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);

Depending on whether your environment allows the spread syntax.

Answer 2

Try with 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 Array.prototype.indexOf isn't defined in IE8 and older, but there are common polyfills for that.