A reduce method which aggregates common data in objects

Question

I built a method using reduce of JS to aggregate together data from a DB in a better shape.

What I'm wondering is, if that method can be simplified with a more modern approach or better written. Like using a different method instead of a reduce.

The method takes the dbData which includes data in the following form:

const dbData = [{
 studyId: 'X',
 siteId: 'A',
 day: '2000-01-01',
 status: 'PENDING_CALLCENTER',
 current: 5,
 total: 17,
 },
 {
 studyId: 'X',
 siteId: 'A',
 day: '2000-01-01',
 status: 'PENDING_SITE',
 current: 3,
 total: 9,
 },
 {
 studyId: 'Y',
 siteId: 'B',
 day: '2000-01-01',
 status: 'PENDING_SITE',
 current: 3,
 total: 9,
 },
 {
 studyId: 'Y',
 siteId: 'B',
 day: '2000-01-01',
 status: 'PENDING_CALLCENTER',
 current: 3,
 total: 9,
 },
]

The data contains two same fields/values as studyId and siteId and what I aggregate is the status, current, total to be included under the same Study and Site.

The output of the above passing via the method:

[
 {
 "studyId": "X",
 "siteId": "A",
 "currents": {
 "PENDING_CALLCENTER": 5,
 "PENDING_SITE": 3
 },
 "totals": {
 "PENDING_CALLCENTER": 17,
 "PENDING_SITE": 9
 }
 },
 {
 "studyId": "Y",
 "siteId": "B",
 "currents": {
 "PENDING_SITE": 6,
 "PENDING_CALLCENTER": 3
 },
 "totals": {
 "PENDING_SITE": 18,
 "PENDING_CALLCENTER": 9
 }
 }
] 

So it is reduced to a different form where we have one object per studyId and siteId which includes the currents and totals of the status.

The method

dbData.reduce((acc, row) => {
const {
 studyId,
 siteId,
 status,
 current,
 total
} = row;
const idx = acc.findIndex(x => studyId === x.studyId && siteId === x.siteId);
const item = idx === -1 ? {
 studyId,
 siteId,
 currents: {},
 totals: {}
} : { ...acc[idx]
};
item.currents[status] = item.currents[status] ? item.currents[status] + current : current;
item.totals[status] = item.totals[status] ? item.totals[status] + total : total;
if (idx === -1) {
 acc.push(item);
} else {
 acc[idx] = item;
}
return acc;
}, []);

A working example

const dbData = [{
 studyId: 'X',
 siteId: 'A',
 day: '2000-01-01',
 status: 'PENDING_CALLCENTER',
 current: 5,
 total: 17,
 },
 {
 studyId: 'X',
 siteId: 'A',
 day: '2000-01-01',
 status: 'PENDING_SITE',
 current: 3,
 total: 9,
 },
 {
 studyId: 'Y',
 siteId: 'B',
 day: '2000-01-01',
 status: 'PENDING_SITE',
 current: 3,
 total: 9,
 },
 {
 studyId: 'Y',
 siteId: 'B',
 day: '2000-01-01',
 status: 'PENDING_CALLCENTER',
 current: 3,
 total: 9,
 },
];
const reduced = dbData.reduce((acc, row) => {
 const {
 studyId,
 siteId,
 status,
 current,
 total
 } = row;
 const idx = acc.findIndex(x => studyId === x.studyId && siteId === x.siteId);
 const item = idx === -1 ? {
 studyId,
 siteId,
 currents: {},
 totals: {}
 } : { ...acc[idx]
 };
 item.currents[status] = item.currents[status] ? item.currents[status] + current : current;
 item.totals[status] = item.totals[status] ? item.totals[status] + total : total;
 if (idx === -1) {
 acc.push(item);
 } else {
 acc[idx] = item;
 }
 return acc;
}, []);
console.log(reduced);

Answer 1

A couple of things that can be simplified/refactored:

• Conditionals can be reduced to improve code readability.
• No need to clone an object if it already exists. Instead, we can just update the currents and totals properties.

const dbData = [{
 studyId: 'X',
 siteId: 'A',
 day: '2000-01-01',
 status: 'PENDING_CALLCENTER',
 current: 5,
 total: 17,
 },
 {
 studyId: 'X',
 siteId: 'A',
 day: '2000-01-01',
 status: 'PENDING_SITE',
 current: 3,
 total: 9,
 },
 {
 studyId: 'Y',
 siteId: 'B',
 day: '2000-01-01',
 status: 'PENDING_SITE',
 current: 3,
 total: 9,
 },
 {
 studyId: 'Y',
 siteId: 'B',
 day: '2000-01-01',
 status: 'PENDING_CALLCENTER',
 current: 3,
 total: 9,
 },
];
const reduced = dbData.reduce((acc, row) => {
 const {
 studyId,
 siteId,
 status,
 current,
 total
 } = row;
 
 const idx = acc.findIndex(x => studyId === x.studyId && siteId === x.siteId);
 
 if (idx === -1) {
 const item = {
 studyId,
 siteId,
 currents: {
 [status]: current, 
 },
 totals: {
 [status]: total,
 },
 };
 
 acc.push(item);
 } else {
 acc[idx].currents[status] = (acc[idx].currents[status] || 0) + current;
 acc[idx].totals[status] = (acc[idx].totals[status] || 0) + total;
 }
 
 return acc;
}, []);
console.log(reduced);