JS: Flatten and Reduce Array of Objects with Multiple Properties and Combine Values

Question

I have been stuck on this for a little while now, but I'm unsure on how I can flatten and reduce the below example data into unique key value pairs with the value being combined if there are multiples of the same key.

Example:

const data = [
  { test: 200 },
  { test2: 300, test3: 100 },
  { test3: 400, test4: 150, test2: 50 },
];

Expected result:

const result = [
    { test: 200 }, 
    { test2: 350 }, 
    { test3: 500 }, 
    { test4: 150 }
];

Any ideas?

TIA

@TannerDolby I guess its slightly related but Im still unsure on how to combine the values — yush
– yush, Commented Mar 9, 2022 at 22:55

EkkoKo · Accepted Answer · 2022-03-09 23:24:08Z

1

Try this:

const data = [
  { test: 200 },
  { test2: 300, test3: 100 },
  { test3: 400, test4: 150, test2: 50 }
];

const flattenedAndReduced = data.reduce((prev, current) => {
  Object.keys(prev).forEach((key, index) => {
    if (current[key]) {
      prev[key] += current[key];
      delete current[key];
    }
  });
  Object.keys(current).forEach((key) => {
    if (!prev[key]) prev[key] = current[key];
  });
  return { ...prev };
});

const flattenedAndReducedToArray = Object.keys(flattenedAndReduced).map((key) => ({
  [key]: flattenedAndReduced[key]
}));

answered Mar 9, 2022 at 23:24

EkkoKo

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