How do I sort array objects and manipulate them to return a new 2D array?

Question

I have the following code:

var testArrys = [
{ attrName: 'life', p_id:19, num:1, name: 'milk'},
{ attrName: 'food', p_id:20, num:1, name: 'apple'},
{ attrName: 'life', p_id:19, num:2, name: 'milk'},
{ attrName: 'life', p_id:22, num:1, name: 'egg'},
{ attrName: 'clothes', p_id:21, num:1, name: 'coat'},
]

Divide the different arrays according to attrName, add num according to whether p_id is the same, Delete more than p_id objects

I tried the following:

function groupBy(list, keyGetter) {
    const map = new Map();
    list.forEach((item) => {
         const key = keyGetter(item);
         const collection = map.get(key);
         if (!collection) {
             map.set(key, [item]);
         } else {
             collection.push(item);
         }
    });
    return map;
}
const grouped = groupBy(testArrys, attr => attr.attrName);

I tried, but I couldn't achieve what I wanted

I want the following results：

var result = [
  [
    { attrName: 'life', p_id:19, num:3, name: 'milk'},
    { attrName: 'life', p_id:22, num:1, name: 'egg'},
  ],
  [
    { attrName: 'food', p_id:20, num:1, name: 'apple'}
  ],
  [
    { attrName: 'clothes', p_id:21, num:1, name: 'coat'}
  ],
]

Possible duplicate of How do I sort array objects and return a new 2D array? — shrys
– shrys, Commented Aug 14, 2019 at 6:19

Nina Scholz · Accepted Answer · 2019-08-14 06:53:56Z

2

You could check for the same p_id in the collection and add num value to the existing property. By mutating the object, I suggest to use a copy of item.

At the end, return the values from the Map.

For a dynamic approach, you could specify a function for getting the item with the wanted sub key in the same group and perform either the same property or different, depending on the find.

function groupBy(list, keyGetter, sub) {
    const map = new Map();
    list.forEach(({ ...item }) => {
         const key = keyGetter(item);
         const collection = map.get(key);
         if (!collection) {
             map.set(key, [item]);
             return;
         }
         if (!sub) {
             collection.push(item);
             return;
         }
         var temp = collection.find(o => sub.key(o) === sub.key(item));
         if (temp) {
             sub.same(item, temp);
         } else {
             sub.different(item, collection);
         }
    });
    return Array.from(map.values()); // return values only
}

var testArrys = [{ attrName: 'life', p_id:19, num:1, name: 'milk' }, { attrName: 'food', p_id:20, num:1, name: 'apple' }, { attrName: 'life', p_id:19, num:2, name: 'milk' }, { attrName: 'life', p_id:22, num:1, name: 'egg' }, { attrName: 'clothes', p_id:21, num:1, name: 'coat' }]

const
    grouped = groupBy(
        testArrys,
        attr => attr.attrName,
        {
            key: item => item.p_id,
            same: (source, target) => target.num += source.num,
            different: (source, target) => target.push(source)
        }
    );

console.log(grouped);

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

edited Aug 14, 2019 at 6:53

answered Aug 14, 2019 at 6:28

Nina Scholz

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2 Comments

arizafar Over a year ago

OP wants to add up the num if attrName and p_id are same.

BaiClassmate Xiao Over a year ago

@NinaScholz Thank you very much for the answer, what if I want to add a new parameter dynamically?

arizafar · Accepted Answer · 2019-08-14 06:53:43Z

You can use Array.prototype.reduce.

const testArrys = [
	{ attrName: 'life', p_id: 19, num: 1, name: 'milk' },
	{ attrName: 'food', p_id: 20, num: 1, name: 'apple' },
	{ attrName: 'life', p_id: 19, num: 2, name: 'milk' },
	{ attrName: 'life', p_id: 22, num: 1, name: 'egg' },
	{ attrName: 'clothes', p_id: 21, num: 1, name: 'coat' },
]

let out = [...testArrys.reduce((acc, curr) => {
	if (acc.has(curr.attrName)) {
		if (acc.get(curr.attrName)[0].p_id === curr.p_id) {
			acc.set(curr.attrName, [{ ...curr, num: acc.get(curr.attrName)[0].num + curr.num }]);
		} else {
			acc.get(curr.attrName).push(curr)
		}
	} else {
		acc.set(curr.attrName, [curr])
	}
	return acc;
}, new Map()).values()];

console.log(out)

If you want to use multiple parameters for merging you use Array.prototype.every to check if values for each key matches then only merge.

const testArrys = [
	{ attrName: 'life', p_id: 19, num: 1, name: 'milk' },
	{ attrName: 'food', p_id: 20, num: 1, name: 'apple' },
	{ attrName: 'life', p_id: 19, num: 2, name: 'milk' },
	{ attrName: 'life', p_id: 22, num: 1, name: 'egg' },
	{ attrName: 'clothes', p_id: 21, num: 1, name: 'coat' },
]

let out = [...testArrys.reduce((acc, curr) => {
	if (acc.has(curr.attrName)) {
		if (checkEqual(acc.get(curr.attrName)[0], curr, ['p_id', 'name'])) {
			acc.set(curr.attrName, [{ ...curr, num: acc.get(curr.attrName)[0].num + curr.num }]);
		} else {
			acc.get(curr.attrName).push(curr)
		}
	} else {
		acc.set(curr.attrName, [curr])
	}
	return acc;
}, new Map()).values()];

function checkEqual(a, b, keys) {
	return keys.every(k=> a[k]=== b[k])
}
console.log(out)

Eslam Abu Hugair · Accepted Answer · 2019-08-14 07:06:30Z

0

 Object.values(testArrys.reduce((items , item)=>{
  if(items[item.attrName])
    items[item.attrName].push(item)
  else
   items[item.attrName]= [item]

  return items
}
,{}))

answered Aug 14, 2019 at 7:06

Eslam Abu Hugair

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