Run results for: JSON.stringify vs structuredClone vs customClone

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:139.0) Gecko/20100101 Firefox/139.0

Browser: Firefox 139

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
✓ customClone	12,339,389 Ops/sec
JSON.stringify	1,656,047 Ops/sec
structuredClone	1,300,236 Ops/sec

Script Preparation code:

var customClone = function customClone(val) {
  var k, out, tmp;

  if (Array.isArray(val)) {
    out = Array(k = val.length);
    while (k--) out[k] = (tmp = val[k]) !== null && typeof tmp === 'object' ? customClone(tmp) : tmp;
    return out;
  }

  if (val !== null && typeof val === 'object') {
    out = {}; // null
    for (k in val) {
      if (k !== '__proto__') {
        out[k] = (tmp = val[k]) !== null && typeof tmp === 'object' ? customClone(tmp) : tmp;
      }
    }
    return out;
  }

  return val;
}

var MyObject = {
  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.stringify
myCopy = JSON.parse(JSON.stringify(MyObject));
structuredClone
myCopy = structuredClone(MyObject);
customClone
myCopy = customClone(MyObject);