按数组中的多个键对对象值数组求和

Question

Suppose I have:

const arr = [
    {'name': 'P1','value': 150, 'nn': 2},
    {'name': 'P1','value': 150, 'nn': 3},
    {'name': 'P2','value': 200, 'nn': 5},
    {'name': 'P3','value': 450, 'nn': 1}
]
const keysToSum = ['value', 'nn' ]

and I want:

[
  { name: 'P1', value: 300, nn: 5 },
  { name: 'P2', value: 200, nn: 5 },
  { name: 'P3', value: 450, nn: 1 }
]

So I want to sum the values inside the keys value and nn (because these keys are in keysToSum ) if name is the same. How can I do that?

I know I can use reduce , for example:

const result = arr.reduce((acc, val) => {
    const o = acc.filter((obj) => {
        return obj.name == val.name;
    }).pop() || {name: val.name, value: 0};
    
    o.value += val.value;
    acc.push(o);
    return acc;
},[])

But this piece of code works with only a key (value in that case), how can generalize it using keysToSum ?

 const arr = [ {'name': 'P1','value': 150, 'nn': 2}, {'name': 'P1','value': 150, 'nn': 3}, {'name': 'P2','value': 200, 'nn': 5}, {'name': 'P3','value': 450, 'nn': 1} ]; const result = arr.reduce((acc, val) => { const o = acc.filter((obj) => { return obj.name == val.name; }).pop() || {name: val.name, value: 0}; o.value += val.value; acc.push(o); return acc; },[]); console.log(result)

Answer 1

You could reduce the array by using an object and iterate the wanted keys for summing property values.

 const array = [{ name: 'P1', value: 150, nn: 0 }, { name: 'P1', value: 150, nn: 3 }, { name: 'P2', value: 200, nn: 2 }, { name: 'P3', value: 450, nn: 5 }], keysToSum = ['value', 'nn'], result = Object.values(array.reduce((r, { name, ...o }) => { if (!r[name]) r[name] = { name }; keysToSum.forEach(k => r[name][k] = (r[name][k] || 0) + o[k]); return r; }, [])); console.log(result);

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Answer 2

Using reduce with an object that uses the name as a key, you can easily keep track of the objecs with dupe and increment the properties.

 const arr = [ {'name': 'P1','value': 150, 'nn': 0}, {'name': 'P1','value': 150, 'nn': 3}, {'name': 'P2','value': 200, 'nn': 2}, {'name': 'P3','value': 450, 'nn': 5} ] const keysToSum = ['value', 'nn' ] const summed = Object.values(arr.reduce((obj, record) => { // have we seen this name yet? If not copy the record if (!obj[record.name]) { obj[record.name] = { ...record }; } else { // if we saw it, sum the fields we care about keysToSum.forEach(key => { obj[record.name][key] += record[key]; }) } return obj }, {})); console.log(summed)