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javascriptarraysreducehigher-order-functions
Kannan T
Kannan T

Reputation: 1749

Using Higher order functions instead of two loops

I wanted to use higher order functions such as Map, Filter, Reduce.
My problem is I have an array which is not organised so I had to perform a loop operation to get the result I wanted. An array has two fields one is _id and totalCount which is an array the length will be minimum 0 to 3.
The totalCount each iteration consists of two fields one is orderstatus and another is total I want to perform a normal if else condition if orderstatus is "Merchant" or "driver" or "user" I want to take that iterated total and store it in my array like MerchantCount.

This is my code:

var arr = [{
   _id: "2017-12-08",
   totalcount: [{
     orderstatus: "MERCHANT",
     total: 1
   }]
 },
 {
   _id: "2017-12-02",
   totalcount: [{
     orderstatus: "USER",
     total: 2
   }]
 },
 {
   _id: "2017-12-06",
   totalcount: [{
     orderstatus: "DRIVER",
     total: 1
   }]
 },
 {
   _id: "2017-12-07",
   totalcount: [{
     orderstatus: "MERCHANT",
     total: 3
   }]
 },
 {
   _id: "2017-12-04",
   totalcount: [{
       orderstatus: "DRIVER",
       total: 1
     },
     {
       orderstatus: "MERCHANT",
       total: 2
     },
     {
       orderstatus: "USER",
       total: 1
     }
   ]
 }
]

The loop am performing:

for (let i = 0; i < recentUserCount.length; i++) {
  for (let j = 0; j < recentUserCount[i].totalcount.length; j++) {
    if (recentUserCount[i].totalcount[j].usertype == "DRIVER") {
      recentUserCount[i].DRIVERCount = recentUserCount[i].totalcount[j].total;
    } else if (recentUserCount[i].totalcount[j].usertype == "USER") {
      recentUserCount[i].USERCount = recentUserCount[i].totalcount[j].total;
    } else if (recentUserCount[i].totalcount[j].usertype == "MERCHANT") {
      recentUserCount[i].MERCHANTCount = recentUserCount[i].totalcount[j].total;
    }
  }
}

The result will be roughly like below:

    0 : {_id: "2017-12-08", totalcount: Array(1), MERCHANTCount: 3, $$hashKey: "object:316"}
    1 : {_id: "2017-12-07", totalcount: Array(1), MERCHANTCount: 3, $$hashKey: "object:317"}
    2 : {_id: "2017-12-06", totalcount: Array(1), DRIVERCount: 1, $$hashKey: "object:318"}
    3 : {_id: "2017-12-04", totalcount: Array(3), DRIVERCount: 1, MERCHANTCount: 2, USERCount: 1, …}

I want the same operation to be performed using Map/Filter or Reduce method.

Upvotes: 0

Views: 619

Answers (3)

ttncrch
ttncrch

Reputation: 7253

Pretty easy with ES6 syntax and map/reduce, Full functional snippet:

var arr = [{_id:"2017-12-08",totalcount:[{orderstatus:"MERCHANT",total:1}]},{_id:"2017-12-02",totalcount:[{orderstatus:"USER",total:2}]},{_id:"2017-12-06",totalcount:[{orderstatus:"DRIVER",total:1}]},{_id:"2017-12-07",totalcount:[{orderstatus:"MERCHANT",total:3}]},{_id:"2017-12-04",totalcount:[{orderstatus:"DRIVER",total:1},{orderstatus:"MERCHANT",total:2},{orderstatus:"USER",total:1}]}];

  const result = arr
      .map(({_id, totalcount}) => ({
        totalcount,
        _id,
        ...totalcount.reduce((acc, {orderstatus, total}) => 
          ({...acc, [`${orderstatus}count`]: total}), {})
        }))

console.log(result)

https://jsbin.com/kiwalozuxa/edit?html,js,console,output

EDIT: The spread operator (...) is used to spread the keys/values of an objet (or values of an array). totcalcount.reduce here return an object:

{
  x: "x",
  y: "y"
}

Since it's not technically valid in javascript to have an objet of this form:

{
  a: "a",
  b: "b",
  {
    x: "x",
    y: "y"
  }
}

I use the spread operator to merge my "child" object into the parent objet and produce:

{
  a: "a",
  b: "b",
  x: "x",
  y: "y"
}

I use the same technique in the reducer.

Upvotes: 4

Nina Scholz
Nina Scholz

Reputation: 386680

You could shrink it to two nested forEach loops and take orderstatus as part of the new property.

var totalReference = { MERCHANT: 'MERCHANTCount', USER: 'USERCount', DRIVER: 'DRIVERCount' },
    array = [{ _id: "2017-12-08", totalcount: [{ orderstatus: "MERCHANT", total: 1 }] }, { _id: "2017-12-02", totalcount: [{ orderstatus: "USER", total: 2 }] }, { _id: "2017-12-06", totalcount: [{ orderstatus: "DRIVER", total: 1 }] }, { _id: "2017-12-07", totalcount: [{ orderstatus: "MERCHANT", total: 3 }] }, { _id: "2017-12-04", totalcount: [{ orderstatus: "DRIVER", total: 1 }, { orderstatus: "MERCHANT", total: 2 }, { orderstatus: "USER", total: 1 }] }];

array.forEach(function (o) {
    o.totalcount.forEach(function (p) {
        if (totalReference[p.orderstatus]) {
            o[totalReference[p.orderstatus]] = p.total;
         }
    });
});

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

Upvotes: 0

baao
baao

Reputation: 73251

I'd reduce and assign it

let res = arr.reduce((a, b) => {
    let totals = b.totalcount.reduce((x, y) => {
        x[y.orderstatus + 'Count'] = (x[y.orderstatus + 'Count'] || 0) + y.total;
        return x;
    }, {});
    return a.concat(Object.assign(b, totals));
}, []);


var arr = [{_id:"2017-12-08",totalcount:[{orderstatus:"MERCHANT",total:1}]},{_id:"2017-12-02",totalcount:[{orderstatus:"USER",total:2}]},{_id:"2017-12-06",totalcount:[{orderstatus:"DRIVER",total:1}]},{_id:"2017-12-07",totalcount:[{orderstatus:"MERCHANT",total:3}]},{_id:"2017-12-04",totalcount:[{orderstatus:"DRIVER",total:1},{orderstatus:"MERCHANT",total:2},{orderstatus:"USER",total:1}]}];

let res = arr.reduce((a, b) => {
    let totals = b.totalcount.reduce((x, y) => {
        x[y.orderstatus + 'Count'] = (x[y.orderstatus + 'Count'] || 0) + y.total;
        return x;
    }, {});
    return a.concat(Object.assign(b, totals));
}, []);

console.log(res);

Upvotes: 1

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