Javascript merging duplicates in an array of objects

Question

I have an array of objects like this-

    {"zone":"lobby a","time":"00:00","hub":"I","Sum":0.0,"schedule":"2022"},
    {"zone":"lobby b","time":"00:01","hub":"I","Sum":1.0,"schedule":"112022"},
    {"zone":"lobby a","time":"00:01","hub":"I","Sum":2.0,"schedule":"11_2022"},
    {"zone":"lobby b","time":"00:03","hub":"I","Sum":0.0,"schedule":"11_2022"},
    {"zone":"lobby c","time":"00:04","hub":"I","Sum":1.0,"schedule":"11_2022"},
    {"zone":"lobby c","time":"00:04","hub":"I","Sum":2.0,"schedule":"11_2022"},

The duplicate 'time' needs to be merged by adding the sums only if the zone is same.

Result should be

    {"zone":"lobby a","time":"00:00","hub":"I","Sum":0.0,"schedule":"2022"},
    {"zone":"lobby b","time":"00:01","hub":"I","Sum":1.0,"schedule":"112022"},
    {"zone":"lobby a","time":"00:01","hub":"I","Sum":2.0,"schedule":"11_2022"},
    {"zone":"lobby b","time":"00:03","hub":"I","Sum":0.0,"schedule":"11_2022"},
    {"zone":"lobby c","time":"00:04","hub":"I","Sum":3.0,"schedule":"11_2022"},

Any help will be much appreciated. I have tried many options using maps etc, but have not been successful.

Does this answer your question? How can I merge properties of two JavaScript objects dynamically? — ericmp, Commented Oct 10, 2022 at 11:53

Ben Aston · Accepted Answer · 2022-10-10 12:35:35Z

The following function uses a grouping function to associate items with one another, and a merging function to perform the addition of the sums.

For each item in the data, the group is determined and the group is replaced by the result of the existing group merged with the current item in that group.

Time complexity is O(n) (one iteration to group the items, one iteration to enumerate the resulting grouped items).

const data = [
    {"zone":"lobby a","time":"00:00","hub":"I","Sum":0.0,"schedule":"2022"},
    {"zone":"lobby b","time":"00:01","hub":"I","Sum":1.0,"schedule":"112022"},
    {"zone":"lobby a","time":"00:01","hub":"I","Sum":2.0,"schedule":"11_2022"},
    {"zone":"lobby b","time":"00:03","hub":"I","Sum":0.0,"schedule":"11_2022"},
    {"zone":"lobby c","time":"00:04","hub":"I","Sum":1.0,"schedule":"11_2022"},
    {"zone":"lobby c","time":"00:04","hub":"I","Sum":2.0,"schedule":"11_2022"} ]

function groupAndMerge(data, groupFn, mergeFn) {
    const result = {}
    for(let d of data) {
        result[groupFn(d)] = mergeFn(d, result[groupFn(d)] || { Sum: 0 }) 
    }
    return Object.values(result)
}

const groupFn = ({zone, time}) => zone + time
const mergeFn = (a, b) => ({ ...a, Sum: a.Sum + b.Sum })
console.log(groupAndMerge(data, groupFn, mergeFn))

Thank you very much. This worked, The other solutions somehow caused issues on the React states( which I'm setting using this array) — Aditya R, Commented Oct 12, 2022 at 5:59

Hans Murangaza DRCongo · Accepted Answer · 2022-10-10 12:14:40Z

let input = [
{"zone":"lobby a","time":"00:00","hub":"I","Sum":0.0,"schedule":"2022"},
    {"zone":"lobby b","time":"00:01","hub":"I","Sum":1.0,"schedule":"112022"},
    {"zone":"lobby a","time":"00:01","hub":"I","Sum":2.0,"schedule":"11_2022"},
    {"zone":"lobby b","time":"00:03","hub":"I","Sum":0.0,"schedule":"11_2022"},
    {"zone":"lobby c","time":"00:04","hub":"I","Sum":1.0,"schedule":"11_2022"},
    {"zone":"lobby c","time":"00:04","hub":"I","Sum":2.0,"schedule":"11_2022"},
    ]

    let cleared = [];

    input.map((item, index)=>{
    const dupl_index = cleared.findIndex(itm_ =>itm_.zone === item.zone && itm_.time === item.time);
    if(dupl_index === -1){
    cleared.push(item)
    }else{
    cleared[dupl_index].Sum = Number(cleared[dupl_index].Sum + item.Sum).toFixed(1)
    }
    })

    console.log(cleared)

Andrew Parks · Accepted Answer · 2022-10-10 12:49:51Z

const a = [
  {"zone":"lobby a","time":"00:00","hub":"I","Sum":0.0,"schedule":"2022"},
  {"zone":"lobby b","time":"00:01","hub":"I","Sum":1.0,"schedule":"112022"},
  {"zone":"lobby a","time":"00:01","hub":"I","Sum":2.0,"schedule":"11_2022"},
  {"zone":"lobby b","time":"00:03","hub":"I","Sum":0.0,"schedule":"11_2022"},
  {"zone":"lobby c","time":"00:04","hub":"I","Sum":1.0,"schedule":"11_2022"},
  {"zone":"lobby c","time":"00:04","hub":"I","Sum":2.0,"schedule":"11_2022"}
];

let r = [];
a.forEach(i => {
  let dup = r.find(j => j.zone===i.zone && j.time===i.time);
  if(dup) dup.Sum = (dup.Sum + i.Sum).toFixed(1);
  else r.push(i);
});
console.log(r);

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