Javascript: Push Object Data into specific index in array and zeroes to rest of the index

Question

I am facing a little issue while inserting object data on specific index in Array.

Here is my JSON

let arr = [ 
        {"days":3, "count" : 10 },
    {"days":4, "count" : 12 },
    {"days":7, "count" : 14 },
    {"days":9, "count" : 20 }

]

Output, I would like to have.

updatedArr = [ 
             {"days":0, "count" : 0 },
             {"days":0, "count" : 0 },
             {"days":3, "count" : 10 },
             {"days":4, "count" : 12 },
             {"days":0, "count" : 0 },
             {"days":6, "count" : 34 },
]

so basically I want the object data to be pushed at specific index based on its key called days.

If the value of days is greater than 5 then it would be a sum of all the days value into one and push that at the last index e.g. 5th index.

Here is the code I have tried.

let arr = [{
    "days": 3,
    "count": 10
},
{
    "days": 4,
    "count": 12
},
{
    "days": 7,
    "count": 14
},
{
    "days": 9,
    "count": 20
}

]

for (let index = 0; index < 6; index++) {
const element = arr[index];


let eachObject = {}

eachObject.count = 0


if (element && element !== undefined && element.days && element.days <= 5) {

    eachObject.days = element.days
    eachObject.count = element.count

    arr.splice((element.days - 1), 0, eachObject)

} else if (element && element !== undefined && element.days > 5) {

    eachObject.days = element.days
    eachObject.count += Number.parseInt(element.count)

    arr.splice(4, 0, eachObject)
} else {
    eachObject.days = 0
    eachObject.count = 0
    arr.push(eachObject)
}

}

Any help would be great.

Thank You.

Nina Scholz · Accepted Answer · 2020-02-12 08:57:19Z

1

You could build a new data set with empty counts and update them with the actual values from the array.

Let start with the accumulator.

This is a new array, using Array.from with a length of 6 items and a mapping of an object with days and count properties.

Array#reduce takes an array and a startValue and returns the changed accumulator for each element.

Inside of the callback, an adjustment for the days property is made for greater value.

An update takes place for some properties of the element. Finally the accumulator r is returned.

let array = [{ days: 3, count: 10 }, { days: 4, count: 12 }, { days: 7, count: 14 }, { days: 9, count: 20 }],
    maxDays = 6,
    result = array.reduce(
        (r, { days, count }) => {
            days = Math.min(days, maxDays);
            r[days - 1].days = days;
            r[days - 1].count += count;
            return r;
        },
        Array.from({ length: maxDays }, () => ({ days: 0, count: 0 }))
    );

console.log(result);

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

edited Feb 12, 2020 at 8:57

answered Feb 10, 2020 at 11:28

Nina Scholz

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6 Comments

Akhil Aravind Over a year ago

can you please explain this solution step by step.

Xperia Reno Over a year ago

thank you for your answer. Days would be started from 1 upto 2,3,4,5,5+ so I guess there will be 1 index shifting in array.

Xperia Reno Over a year ago

thank you for your answer. sometimes I get errors as days undefined even though I get days key in data.

Xperia Reno Over a year ago

@NinaScholz. it's because of Array.from({ length: 6 } . I might get days greater than 6 even sometimes 50 days. so How can I solve this ? Thank You.

Nina Scholz Over a year ago

please add some date with more than 6 days and the wanted result from it.

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