What's the most effecient way to combine this collection?

Question

Given the following collection, what would be the best way to consolidate this data to group by room and make the "names" an array; excluding duplicates, and do not want to use the call the key "name" to make it more dynamic if there are more fields:

var roomAssignments = [{
    room: 'Foo',
    name: 'Fooname',
    other: 'Other'
},{
    room: 'Bar',
    name: 'Barname',,
    other: 'OtherBar'
},{
    room: 'Foo',
    name: 'Baz',,
    other: 'Other'
},{
    room: 'Foo',
    name: 'Baz',,
    other: 'Other'
},{
    room: 'Foo',
    name: 'Bat',,
    other: 'Other'
}];

Desired output:

[{
    room: 'Foo',
    name: [ 'Fooname', 'Baz', 'Bat' ],
    other: ['Other']
}, {
    room: 'Bar',
    name: [ 'Barname' ],
    other: ['OtherBar']
}]

I'm using lodash currently and would prefer that or plain javascript. I think I've been looking at this too long and what I have has about 30 keys that need to be combined into arrays, and I'm looking for the most efficient way to combine all keys into arrays dynamically.

Possible duplicate of [Group array items using object](https://stackoverflow.com/questions/31688459/group-array-items-using-object) — Ishwar Patil, Mar 09 '18 at 12:02
I'm stuck in trying to group each key into an array dynamically. I don't want to use "name" to reduce them, so I'd like to be able to group by "room" and combine each key into an array. — harryBundles, Mar 09 '18 at 12:44

Ele · Accepted Answer · 2018-03-09T14:34:09.710

1

You can use the function reduce and the function includes to discard duplicate values.

var roomAssignments = [{    room: 'Foo',    name: 'Fooname',    other: 'Other'},{    room: 'Bar',    name: 'Barname',    other: 'OtherBar'},{    room: 'Foo',    name: 'Baz',    other: 'Other'},{    room: 'Foo',    name: 'Baz',    other: 'Other'},{    room: 'Foo',    name: 'Bat',    other: 'Other'}],
    result = Object.values(roomAssignments.reduce(function(a, c) {
  if (a[c.room]) {
    Object.keys(c).forEach(function(k) {
      if (k === 'room') return;      
      if (a[c.room][k]) {
        if (!a[c.room][k].includes(c[k])) a[c.room][k].push(c[k]);
      } else a[c.room][k] = [c[k]];
    });
  } else { 
    a[c.room] = { room: c.room };
    Object.keys(c).forEach(function(k) {
      if (k === 'room') return;      
      a[c.room][k] = [c[k]];
    });
  }
  
  return a
}, {}));

console.log(result);

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

edited Mar 09 '18 at 14:34

answered Mar 09 '18 at 12:01

Ele

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How would you reduce each key without actually calling it out? I'd prefer to not use the "name" and group all keys that may be in the object. – harryBundles Mar 09 '18 at 12:35
"message": "SyntaxError: invalid property id", "filename": "https://stacksnippets.net/js", "lineno": 26, "colno": 33 } – harryBundles Mar 09 '18 at 14:05
@harryBundles that error is not related to my code snippet. Try to run it in another browser. – Ele Mar 09 '18 at 14:06
Well, unfortunately I'm working in an intranet environment where my browsers are mostly outdated. While I appreciate the modern approach, I'm forced to keep it ES6 to support older browsers. – harryBundles Mar 09 '18 at 14:26
I updated the code to use lodash to replace the ES7 stuff that didn't work in my lowest supported browser. Thanks for helping me with this! – harryBundles Mar 09 '18 at 18:10

THEtheChad · Answer 2 · 2018-03-09T15:06:26.610

"Efficient" is kind of subjective. The following code is fairly efficient but, more importantly, it's nicer to look at.

var rooms = {};
roomAssignments.forEach(assignment => {
    var title = assignment.room;

    // grab existing room from our rooms map
    // if it doesn't exist, create it
    var room = rooms[title] || (rooms[title] = {room: title});

    for(var k in assignment){

      // skip the room key (it's our room title)
      if(k === 'room') continue;

      var value = assignment[k];

      // grab the existing field from the room object
      // if it doesn't exist, create it
      var field = room[k] || (room[k] = []);

      // see if the value already exists
      // if not, push it
      if(field.indexOf(value) === -1) field.push(value);
    }
})

What's the most effecient way to combine this collection?

2 Answers2