Run results for: Merging Objects

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.82 Safari/537.36

Browser: Chrome 93

Operating system: Mac OS X 10.13.6

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
Reduce / Spread	347.5 Ops/sec
Assign / Single spread	24260.4 Ops/sec
fromEntries / Entries	2863.1 Ops/sec

Script Preparation code:

function createSlices(numSlices, propsPerSlice = 5) {
  const arr = [];

  for (let i = 0; i < numSlices; i++) {
    const o = {};
    for (let j = 0; j < propsPerSlice; j++) {
      o[`key_${i}_${j}`] = `${i}_${j}`;
    }
    arr.push(o);
  }

  return arr;
}

var slices = createSlices(100);

Tests:

Reduce / Spread
slices.reduce((store, slice) => ({ ...store, ...slice }), {});
Assign / Single spread
Object.assign({}, ...slices);
fromEntries / Entries
Object.fromEntries( slices .map((slice) => Object.entries(slice)) .flat() );
Assign / Mutate first obj
slices.unshift({}); Object.assign(...slices);

Run results for: Merging Objects

Reduce / Spread

Assign / Single spread

fromEntries / Entries

Assign / Mutate first obj