Run results for: JSON.stringify + JSON.parse vs structuredClone vs fast_deep_clone (recursive)

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_7 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/26.5 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 26

Operating system: iOS 18.7

Device Platform: Mobile

Date tested: 2 months ago

Benchmark engine: Benchmark.js

fast_deep_clone()

12.9M/s

JSON.parse(JSON.stringify())

4.0M/s

structuredClone()

1.3M/s

View exact numbers

Test name	Executions per second
✓ fast_deep_clone()	12,933,825 Ops/sec
JSON.parse(JSON.stringify())	4,003,523 Ops/sec
structuredClone()	1,289,637 Ops/sec

Script Preparation code:

var obj = {
  description: 'Creates a deep copy of source, which should be an object or an array.',
  myNumber: 123456789,
  myBoolean: true,
  jayson: {
    stringify: 'JSON.stringify() method converts a JavaScript value to a JSON string....',
    parse: 'JSON.parse() method parses a JSON string...'
  }
};

var myCopy = null;

Tests:

JSON.parse(JSON.stringify())
JSON.parse(JSON.stringify(obj));
structuredClone()
structuredClone(obj);
fast_deep_clone()
const fast_deep_clone = (obj) => { function cloneArray(a, fn) { var keys = Object.keys(a); var a2 = new Array(keys.length) for (const key of keys) { var k = keys[key]; var cur = a[k]; if (typeof cur !== 'object' || cur === null) { a2[k] = cur; } else { a2[k] = fn(cur); } } return a2; } if (typeof obj !== 'object' || obj === null) return obj; if (obj instanceof Date) return new Date(obj); if (Array.isArray(obj)) return cloneArray(obj, fast_deep_clone); if (obj.toString() !== '[object Object]') { return obj.toString(); } let value, key; const keys = Object.keys(obj); const outObject = {}; for (key of keys) { if (key) { value = obj[key]; outObject[key] = fast_deep_clone(value); } } return outObject; }; fast_deep_clone(obj);