Filter Array of object based in duplicate keys
I would create a composed key for the key fields and translate the time to a number of milliseconds and then sort by those two elements. In a second step group those entries that have the same key and are at most 1 minute apart:
var transac = [{id: 3,sourceAccount: 'A',targetAccount: 'B',amount: 100,category: 'eating_out',time: '2018-03-02T10:34:30.000Z'},{id: 1,sourceAccount: 'A',targetAccount: 'B',amount: 100,category: 'eating_out',time: '2018-03-02T10:33:00.000Z'},{id: 6,sourceAccount: 'A',targetAccount: 'C',amount: 250,category: 'other',time: '2018-03-02T10:33:05.000Z'},{id: 4,sourceAccount: 'A',targetAccount: 'B',amount: 100,category: 'eating_out',time: '2018-03-02T10:36:00.000Z'},{id: 2,sourceAccount: 'A',targetAccount: 'B',amount: 100,category: 'eating_out',time: '2018-03-02T10:33:50.000Z'},{id: 5,sourceAccount: 'A',targetAccount: 'C',amount: 250,category: 'other',time: '2018-03-02T10:33:00.000Z'}];
const result = transac.map(t => ({
key: JSON.stringify([t.sourceAccount, t.targetAccount, t.amount, t.category]),
epoch: Date.parse(t.time),
t
})).sort((a,b) =>
a.key.localeCompare(b.key) || a.epoch - b.epoch || a.t.id - b.t.id
).reduce(([acc, prev], curr) => {
if (!prev || curr.key != prev.key || curr.epoch - prev.epoch > 60000) acc.push([]);
acc[acc.length-1].push(curr.t);
return [acc, curr];
}, [[]])[0];
console.log(result);Following up on a comment below, the above result includes all transactions. The ones that have "duplicates" (according to the definition in the question) are grouped together with their duplicates in sub arrays; those that do not have such duplicates appear alone in their own sub arrays.
So to only get the duplicates, add the appropriate filter:
const duplicates = result.filter(a => a.length > 1);