I am trying to merge an array of objects by summing up the totals of each key-value pair under the totals object. For example, the below array would yield one object with a totals object of 3 apples and 5 oranges. This should be dynamic. If pears were to be a key in another object, the resulting object would include three keys under the totals object: apples, oranges, and pears.
Sample Input:
[
{
summary: {
totals: {
apples: 2,
oranges: 3
}
}
},
{
summary: {
totals: {
apples: 1,
oranges: 2
}
}
}
]
Expected Output:
{
summary:{
totals:{
apples:3,
oranges:5
}
}
}
What I've tried:
function mergeObjects(arr) {
let shape = {
summary:{
totals:{}
}
}
return arr.reduce((prev, cur) => {
if(cur.summary.totals.apples){
shape.summary.totals.apples.push(cur.summary.totals.apples)
}
}, shape);
}
Array#reduce, iterate over the array while updating an objectObject#entries and
, iterate over the current totals pairs and update the accumulator.const arr = [
{ summary: { totals: { apples: 2, oranges: 3 } } },
{ summary: { totals: { apples: 1, oranges: 2 } } },
];
const res = arr.reduce((map, current) => {
const { totals: currentTotals = {} } = current.summary ?? {};
const { totals } = map.summary;
Object.entries(currentTotals).forEach(([ key, value ]) => {
totals[key] = (totals[key] ?? 0) + value;
});
return map;
}, { summary: { totals: {} } });
console.log(res);You can try something like. Just loop through the array and sum up apples and oranges.
const arr = [
{
summary: {
totals: {
apples: 2,
oranges: 3,
},
},
},
{
summary: {
totals: {
apples: 1,
oranges: 2,
},
},
},
];
function mergeObjects(arr) {
let shape = {
summary:{
totals:{
apples:0,
oranges:0
}
}
}
arr.forEach(x => {
if(x.summary.totals.apples){
shape.summary.totals.apples += x.summary.totals.apples;
shape.summary.totals.oranges += x.summary.totals.oranges;
}
});
return shape;
}
let result = mergeObjects(arr);
console.log(result);The second option of the reduce function initializes the value.
And the initialized value can be used in prev!
[1] store the value in prev.
[2] prev can accumulate values. You have to return to use the accumulated value. If not returned, the value will be undefined.
[3] apples is not an array type, so you cannot use the push method. it is a number type, you must use a numeric operator.
function mergeObjects(arr) {
const shape = {
summary: {
totals: {},
},
};
return arr.reduce((prev, cur) => {
const { apples, oranges } = cur.summary.totals;
// [1]
prev.summary.totals.apples
// [3]
? (prev.summary.totals.apples += apples)
: (prev.summary.totals.apples = apples);
prev.summary.totals.oranges
? (prev.summary.totals.oranges += oranges)
: (prev.summary.totals.oranges = oranges);
// [2]
return prev;
}, shape);
}
tips!
const { apples, oranges } = cur.summary.totals;
prev.summary.totals.apples
? (prev.summary.totals.apples += apples)
: (prev.summary.totals.apples = apples);