Run results for: Object.assign vs spread operator vs structured clone vs for loop copy vs JSON duplicate with fallbacks

This test is only intended to be used to test for getting a new reference to an object, not generating a deep clone of an object. Some of the methods used here generate a deep copy and some a shallow copy, but the intent is only to find the fastest method of getting a shallow copy where the key length is long and there are lots of keys.

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser: Chrome 131

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
Get copy using Object.create	1700138.8 Ops/sec
Get copy using spread	14897090.0 Ops/sec
Get copy using structuredClone	370700.4 Ops/sec
Copy manually using for loop	733511.2 Ops/sec
Copy using JSON.stringify	387997.2 Ops/sec

Script Preparation code:

const original = {
  'this is a somewhat long key with many characters0': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters1': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters2': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters3': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters4': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters5': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters6': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters7': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters8': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters9': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters10': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters11': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters12': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters13': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters14': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters15': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters16': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters17': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters18': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters19': 'This is a value of somewhat the same length',
  'this is a somewhat long key with many characters20': 'This is a value of somewhat the same length',
};

Tests:

Get copy using Object.assign
const newVersion = Object.assign({}, original ?? {});
Get copy using spread
const newVersion = { ...(original ?? {}) };
Get copy using structuredClone
const newVersion = structuredClone(original ?? {});
Copy manually using for loop
const newVersion = {}; const keys = Object.keys(original ?? {}); const len = keys.length; for (let i = 0; i < len; i++) { newVersion[keys[i]] = original[keys[i]]; }
Copy using JSON.stringify
const newVersion = JSON.parse(JSON.stringify(original ?? {}));

Run results for: Object.assign vs spread operator vs structured clone vs for loop copy vs JSON duplicate with fallbacks

Get copy using Object.assign

Get copy using spread

Get copy using structuredClone

Copy manually using for loop

Copy using JSON.stringify