poprawione task 2

index.js

function areTransationsTheSame (t1, t2) {
    return t1.sourceAccount === t2.sourceAccount
        && t1.targetAccount === t2.targetAccount
    // ... and the rest
}

export const findDuplicateTransactions = (transactions = []) => {
    const groupedTransactionsMap = transactions
        .map((transaction) => {
            let key = {
                sourceAccount: transaction.sourceAccount,
                targetAccount: transaction.targetAccount,
                category: transaction.category,
                amount: transaction.amount,
            };
            return { k: key, v: transaction };
        })
        .reduce((accumulator, transactionKeyValue) => {
            const stringifiedKey = `${transationKeyValue.sourceAccount};${transationKeyValue.targetAccount}`;

            if (!accumulator.has(stringifiedKey)) {
                accumulator.set(stringifiedKey, [transactionKeyValue.v]);
            } else {
                const current = accumulator.get(stringifiedKey);
                current.push(transactionKeyValue.v);
                // accumulator.set(stringifiedKey, current);
            }

            return accumulator;
        }, new Map());

    const result = [];
    const oneMinuteInMs = 60 * 1000; // 60s * 1000ms
    for (const transactionsGroup of groupedTransactionsMap.values()) {
        transactionsGroup.sort(function (a, b) {
            let timeA = Date.parse(a.time);
            let timeB = Date.parse(b.time);
            return timeA - timeB;
        });

        let resultCandidate = [];
        for (const currentTransaction of transactionsGroup) {
            const timeDiff = Date.parse(currentTransaction.time) - Date.parse(resultCandidate[resultCandidate.length - 1].time);

            if (
                resultCandidate.length >= 1 &&
                timeDiff > oneMinuteInMs
            ) {
                if (resultCandidate.length >= 2) {
                    result.push(resultCandidate);
                }
                resultCandidate = [];
            }
            resultCandidate.push(currentTransaction);
        }
        if (resultCandidate.length >= 2) {
            result.push(resultCandidate);
        }
    }
    result.sort(function (groupA, groupB) {
        let timeGroupA = Date.parse(groupA[0].time);
        let timeGroupB = Date.parse(groupB[0].time);
        return timeGroupA - timeGroupB;
    });
    return result;
};