MeasureThat.net

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

Measure the fastest way to merge objects, without mutation.

Go to the benchmark
Run details:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:94.0) Gecko/20100101 Firefox/94.0
Firefox 94
Mac OS X 10.15
Desktop
3 years ago
Test name Executions per second
Using the spread operator 7086809.5 Ops/sec
Using Object.assign 10193872.0 Ops/sec
Using For-In loop 21776542.0 Ops/sec
Using For-In loop with type checks 8444607.0 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 type checks

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