MeasureThat.net

Run results for: JavaScript spread operator vs Object.assign vs for-in loop safe performance

Measure the fastest way to merge objects, without mutation.

Go to the benchmark
Run details:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Chrome 134
Windows
Desktop
4 days ago
Test name Executions per second
Using the spread operator 37821168.0 Ops/sec
Using Object.assign 28400752.0 Ops/sec
Using For-In loop 57670288.0 Ops/sec
Using For-In loop with hasOwnProperty 31112040.0 Ops/sec
Tests:

  • Using the spread operator

    AخA
     
    const firstObject = { sampleData: 'Hello world' }
    const secondObject = { moreData: 'foo bar' }
    const finalObject = {
        ...firstObject,
        ...secondObject
    };

  • Using Object.assign

     
    const firstObject = { sampleData: 'Hello world' }
    const secondObject = { moreData: 'foo bar' }
    const finalObject = Object.assign({}, firstObject, secondObject);

  • Using For-In loop

     
    const firstObject = { sampleData: 'Hello world' }
    const secondObject = { moreData: 'foo bar' }
    const finalObject = {}
    for (let key in firstObject) {
      finalObject[key] = firstObject[key];
    }
    for (let key in secondObject) {
      finalObject[key] = secondObject[key];
    }

  • Using For-In loop with hasOwnProperty

     
    const firstObject = { sampleData: 'Hello world' }
    const secondObject = { moreData: 'foo bar' }
    const finalObject = {}
    for (let key in firstObject) {
      if (Object.prototype.hasOwnProperty.call(firstObject, key)) {
        finalObject[key] = firstObject[key];
      }
    }
    for (let key in secondObject) {
      if (Object.prototype.hasOwnProperty.call(secondObject, key)) {
        finalObject[key] = secondObject[key];
      }
    }