So I have an array of objects with some varying number of properties (but the property names are known), for example:
let data = [{a: 10, b: 1, c:10},
{a: 17, b: 2, c:16},
{a: 23, b: 3, c:41}]
I need to construct an object that sums up the values in the respective properties, so in this example I'd need to construct an object {a: 50, b: 6, c:67}
I wrote the following function to do this:
calcTotalForDataProps(data, props) {
let summedData = {}
for (const prop of props) {
summedData[prop] = 0;
}
data.forEach((dataObj) => {
for (const prop of props) {
summedData[prop] += dataObj[prop];
}
});
return summedData;
}
And you call it like this:
calcTotalForDataProps(data, ['a', 'b', 'c']);
But I'm wondering if there's a much shorter way to write this with ES6?
You could map the wanted props with their new sums for getting an object as result.
function calcTotalForDataProps(data, props) {
return data.reduce((r, o) => Object
.fromEntries(props.map(k => [k, (r[k] || 0) + o[k]])
), {});
}
const data = [{ a: 10, b: 1, c: 10}, { a: 17, b: 2, c: 16 }, { a: 23, b: 3, c: 41 }]
console.log(calcTotalForDataProps(data, ['a', 'b', 'c']));There's no need to iterate over the properties initially - you can create the property inside the other loop if it doesn't exist yet.
let data = [{a: 10, b: 1, c:10},
{a: 17, b: 2, c:16},
{a: 23, b: 3, c:41}]
const calcTotalForDataProps = (data, props) => {
const summedData = {};
for (const obj of data) {
for (const [prop, num] of Object.entries(obj)) {
summedData[prop] = (summedData[prop] || 0) + num;
}
}
return summedData;
}
console.log(calcTotalForDataProps(data));