file.js

const hashCode = str => str.split('').reduce((prevHash, currVal) =>
  (((prevHash << 5) - prevHash) + currVal.charCodeAt(0)) | 0, 0);
const sortByTime = (trx, nextTrx) => new Date(trx.time) - new Date(nextTrx.time);
const getMinutesFromDates = (startDate, endDate) => {
  const difference = new Date(endDate).getTime() - new Date(startDate).getTime();
  return (difference / 60000);
};

const findDuplicateTransactions = (transactions = []) => {
  let map = new Map();
  transactions.forEach((item) => {
    const hash = hashCode(item.sourceAccount + item.targetAccount + item.category + item.amount);
    if (map.has(hash)) {
      map.get(hash).push(item);
    } else {
      map.set(hash, [item]);
    }
  });

  map = new Map([...map.entries()].sort((a, b) => new Date(a[1][0].time) - new Date(b[1][0].time)));
  let result = [...map.values()];

  result = result.map((arrOfTrx) => {
    arrOfTrx.sort(sortByTime);

    const filterByTime = (trx, index) => {
      let diffMax;
      let diffMin;
      
      if (arrOfTrx[index + 1]) {
        diffMax = getMinutesFromDates(trx.time, arrOfTrx[index + 1].time);
      }
      if (arrOfTrx[index - 1]) {
         diffMin = getMinutesFromDates(arrOfTrx[index - 1].time, trx.time);
      }

      if ((diffMin > 0 && diffMin < 1) || (diffMax > 0 && diffMax < 1)) {
        return true;
      }
      return false;
    };
    arrOfTrx = arrOfTrx.filter(filterByTime);

    return arrOfTrx;
  }).filter((arrOfTrx) => !arrOfTrx.length < 1);

  return result;
};

task.md

Sometimes when a customer is charged, there is a duplicate transaction created. We need to find those transactions so that they can be dealt with. Everything about the transaction should be identical, except the transaction id and the time at which it occurred, as there can be up to a minute delay.

findDuplicateTransactions(transactions)

Find all transactions that have the same sourceAccount, targetAccount, category, amount, and the time difference between each consecutive transaction is less than 1 minute.

Input You can assume that all parameters will always be present and valid. However, the incoming transactions are not guaranteed to be in any particular order.

list of transactions (Transaction[]) Output list of all the duplicate transaction groups, ordered by time ascending (Transaction[][]) The groups should be sorted in ascending order of the first transaction in the group. Example Input transactions:

[ { 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' } ];

Expected output:

[

[

{
  id: 1,
  sourceAccount: "A",
  targetAccount: "B",
  amount: 100,
  category: "eating_out",
  time: "2018-03-02T10:33:00.000Z"
},

{
  id: 2,
  sourceAccount: "A",
  targetAccount: "B",
  amount: 100,
  category: "eating_out",
  time: "2018-03-02T10:33:50.000Z"
},

{
  id: 3,
  sourceAccount: "A",
  targetAccount: "B",
  amount: 100,
  category: "eating_out",
  time: "2018-03-02T10:34:30.000Z"
}

],

[

{

  id: 5,
  sourceAccount: "A",
  targetAccount: "C",
  amount: 250,
  category: "other",
  time: "2018-03-02T10:33:00.000Z"
},

{
  id: 6,
  sourceAccount: "A",
  targetAccount: "C",
  amount: 250,
  category: "other",
  time: "2018-03-02T10:33:05.000Z"
}

]

];

test.js

let assert = require("chai").assert;

describe("findDuplicateTransactions()", function() {
  it("returns empty array if there are no transactions", function() {
    assert.deepEqual(findDuplicateTransactions([]), []);
  });
  
  it("returns empty array if there are no transactions", function() {
    assert.deepEqual(findDuplicateTransactions([
      {
        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'
      }
    ]), [ [ { id: 5,
      sourceAccount: 'A',
      targetAccount: 'C',
      amount: 250,
      category: 'other',
      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: 1,
      sourceAccount: 'A',
      targetAccount: 'B',
      amount: 100,
      category: 'eating_out',
      time: '2018-03-02T10:33:00.000Z' },
    { id: 2,
      sourceAccount: 'A',
      targetAccount: 'B',
      amount: 100,
      category: 'eating_out',
      time: '2018-03-02T10:33:50.000Z' },
    { id: 3,
      sourceAccount: 'A',
      targetAccount: 'B',
      amount: 100,
      category: 'eating_out',
      time: '2018-03-02T10:34:30.000Z' } ] ]);
  });
  
  
   it("returns ordered and grouped array ", function() {
    const inp = [{
      id: 201,
      sourceAccount: 'company_x',
      targetAccount: 'my_account',
      amount: 10000,
      category: 'pension_benefits',
      time: '2018-02-25T08:00:00.000Z',
    },
    {
      id: 39,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -70,
      category: 'eating_out',
      time: '2018-05-15T09:12:20.000Z',
    },
    {
      id: 23,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -70,
      category: 'eating_out',
      time: '2018-04-15T09:12:20.000Z',
    },
    {
      id: 6,
      sourceAccount: 'my_account',
      targetAccount: 'internet_shop',
      amount: -250,
      category: 'other',
      time: '2018-03-01T22:16:40.000Z',
    },
    {
      id: 27,
      sourceAccount: 'company_x',
      targetAccount: 'my_account',
      amount: 10000,
      category: 'salary',
      time: '2018-04-25T08:00:00.000Z',
    },
    {
      id: 1,
      sourceAccount: 'company_x',
      targetAccount: 'my_account',
      amount: 10000,
      category: 'salary',
      time: '2018-02-25T08:00:00.000Z',
    },
    {
      id: 19,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-04-07T09:54:21.000Z',
    },
    {
      id: 14,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-04-01T10:24:40.000Z',
    },
    {
      id: 12,
      sourceAccount: 'my_account',
      targetAccount: 'bowling_place',
      amount: -600,
      category: 'other',
      time: '2018-03-05T21:12:10.000Z',
    },
    {
      id: 41,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -850,
      category: 'groceries',
      time: '2018-05-20T18:51:31.000Z',
    },
    {
      id: 102,
      sourceAccount: 'my_account',
      targetAccount: 'internet_shop',
      amount: -250,
      category: 'other',
      time: '2018-03-01T22:16:50.000Z',
    },
    {
      id: 11,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -1540,
      category: 'groceries',
      time: '2018-03-05T16:24:31.000Z',
    },
    {
      id: 13,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-04-01T10:24:00.000Z',
    },
    {
      id: 25,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -850,
      category: 'groceries',
      time: '2018-04-20T18:51:31.000Z',
    },
    {
      id: 33,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:57:05.000Z',
    },
    {
      id: 36,
      sourceAccount: 'my_account',
      targetAccount: 'internet_shop',
      amount: -1650,
      category: 'other',
      time: '2018-05-08T21:36:41.000Z',
    },
    {
      id: 29,
      sourceAccount: 'my_account',
      targetAccount: 'cinema',
      amount: -580,
      category: 'other',
      time: '2018-05-05T20:01:18.000Z',
    },
    {
      id: 17,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -1870,
      category: 'groceries',
      time: '2018-04-05T10:24:30.000Z',
    },
    {
      id: 7,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -160,
      category: 'groceries',
      time: '2018-03-02T13:14:00.000Z',
    },
    {
      id: 31,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:55:10.000Z',
    },
    {
      id: 24,
      sourceAccount: 'my_account',
      targetAccount: 'fitness_club',
      amount: -610,
      category: 'other',
      time: '2018-04-22T11:54:10.000Z',
    },
    {
      id: 5,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-03-02T09:25:20.000Z',
    },
    {
      id: 4,
      sourceAccount: 'my_account',
      targetAccount: 'cinema',
      amount: -330,
      category: 'other',
      time: '2018-03-01T20:10:15.000Z',
    },
    {
      id: 101,
      sourceAccount: 'company_x',
      targetAccount: 'my_account',
      amount: 240,
      category: 'salary',
      time: '2018-02-25T08:00:30.000Z',
    },
    {
      id: 28,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -1870,
      category: 'groceries',
      time: '2018-05-05T10:24:30.000Z',
    },
    {
      id: 15,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-04-01T10:25:10.000Z',
    },
    {
      id: 10,
      sourceAccount: 'my_account',
      targetAccount: 'fitness_club',
      amount: -560,
      category: 'other',
      time: '2018-03-04T12:54:10.000Z',
    },
    {
      id: 35,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:58:06.000Z',
    },
    {
      id: 38,
      sourceAccount: 'my_account',
      targetAccount: 'restaurant',
      amount: -970,
      category: 'eating_out',
      time: '2018-05-17T19:52:46.000Z',
    },
    {
      id: 3,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -1000,
      category: 'groceries',
      time: '2018-03-01T17:28:32.000Z',
    },
    {
      id: 26,
      sourceAccount: 'my_account',
      targetAccount: 'cinema',
      amount: -450,
      category: 'other',
      time: '2018-04-23T19:13:10.000Z',
    },
    {
      id: 32,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:56:09.000Z',
    },
    {
      id: 21,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -1690,
      category: 'groceries',
      time: '2018-04-10T18:14:10.000Z',
    },
    {
      id: 30,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:54:21.000Z',
    },
    {
      id: 20,
      sourceAccount: 'my_account',
      targetAccount: 'internet_shop',
      amount: -1650,
      category: 'other',
      time: '2018-04-08T21:36:41.000Z',
    },
    {
      id: 16,
      sourceAccount: 'company_x',
      targetAccount: 'my_account',
      amount: 10000,
      category: 'salary',
      time: '2018-03-25T08:10:00.000Z',
    },
    {
      id: 2,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-03-01T12:34:00.000Z',
    },
    {
      id: 9,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-03-04T07:14:20.000Z',
    },
    {
      id: 37,
      sourceAccount: 'my_account',
      targetAccount: 'supermarket',
      amount: -1690,
      category: 'groceries',
      time: '2018-05-10T18:14:10.000Z',
    },
    {
      id: 8,
      sourceAccount: 'my_account',
      targetAccount: 'restaurant',
      amount: -670,
      category: 'eating_out',
      time: '2018-03-02T18:54:45.000Z',
    },
    {
      id: 22,
      sourceAccount: 'my_account',
      targetAccount: 'restaurant',
      amount: -970,
      category: 'eating_out',
      time: '2018-04-17T19:52:46.000Z',
    },
    {
      id: 18,
      sourceAccount: 'my_account',
      targetAccount: 'cinema',
      amount: -580,
      category: 'other',
      time: '2018-04-05T20:01:18.000Z',
    },
    {
      id: 40,
      sourceAccount: 'my_account',
      targetAccount: 'fitness_club',
      amount: -610,
      category: 'other',
      time: '2018-05-22T11:54:10.000Z',
    },
    {
      id: 42,
      sourceAccount: 'my_account',
      targetAccount: 'cinema',
      amount: -450,
      category: 'other',
      time: '2018-05-23T19:13:10.000Z',
    }];


    const out = [[{
      id: 6,
      sourceAccount: 'my_account',
      targetAccount: 'internet_shop',
      amount: -250,
      category: 'other',
      time: '2018-03-01T22:16:40.000Z',
    },
    {
      id: 102,
      sourceAccount: 'my_account',
      targetAccount: 'internet_shop',
      amount: -250,
      category: 'other',
      time: '2018-03-01T22:16:50.000Z',
    }],
    [{
      id: 13,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-04-01T10:24:00.000Z',
    },
    {
      id: 14,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-04-01T10:24:40.000Z',
    },
    {
      id: 15,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -50,
      category: 'eating_out',
      time: '2018-04-01T10:25:10.000Z',
    }],
    [{
      id: 30,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:54:21.000Z',
    },
    {
      id: 31,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:55:10.000Z',
    },
    {
      id: 32,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:56:09.000Z',
    },
    {
      id: 33,
      sourceAccount: 'my_account',
      targetAccount: 'coffee_shop',
      amount: -90,
      category: 'eating_out',
      time: '2018-05-07T09:57:05.000Z',
    }]];

    assert.deepEqual(findDuplicateTransactions(inp), out);


  });
  
  
  // add your tests here
});