Benchmark: Object.assign vs spread v2

Tests:

Spread
var obj = {} for (var i = 0; i < 1000; i++) { obj = { ...obj, [i.toString()]: i } }
Object.assign
var obj = {} for (var i = 0; i < 1000; i++) { obj = Object.assign(obj, { [i.toString()]: i }) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Object.assign

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

LLMs can make mistakes. Check important info.

Let's dive into the benchmark.

**What is being tested?**

The provided JSON represents a benchmark that compares two approaches to creating and updating an object with 1000 properties: `Object.assign` vs the spread operator (`...`). The test cases are running on a user agent (Chrome 68) and measuring the execution speed of each approach.

**Test Cases:**

There are two individual test cases:

1. **Spread**: This test case uses the spread operator (`...`) to create and update an object with 1000 properties. The code snippet is:
```javascript
var obj = {};
for (var i = 0; i < 1000; i++) {
  obj = { ...obj, [i.toString()]: i };
}
```
The spread operator is used here to merge the existing object `obj` with a new property `[i.toString()]` on each iteration of the loop.

2. **Object.assign**: This test case uses the `Object.assign()` method to create and update an object with 1000 properties. The code snippet is:
```javascript
var obj = {};
for (var i = 0; i < 1000; i++) {
  obj = Object.assign(obj, { [i.toString()]: i });
}
```
`Object.assign()` is used here to copy the existing object `obj` and merge it with a new property `[i.toString()]` on each iteration of the loop.

**Library/Feature Used:**

None. Both test cases use standard JavaScript features only.

**Pros/Cons:**

* **Spread operator (`...`)**:
	+ Pros: concise code, easy to read, and write.
	+ Cons: can be slower than `Object.assign()` for large objects (see benchmark results).
* **Object.assign()**:
	+ Pros: generally faster than the spread operator for large objects.
	+ Cons: slightly more verbose code.

**Other Considerations:**

* Both approaches have a time complexity of O(n), where n is the number of properties in the object. However, `Object.assign()` has an additional overhead due to the creation of temporary objects.
* The benchmark results suggest that `Object.assign()` is faster than the spread operator for this specific use case.

**Alternatives:**

If you need to create and update a large object, consider using a library like Lodash or Immutable.js, which provide optimized methods for this purpose. Another option is to use a data structure like a Map, which can be more efficient than an object for large datasets.

That's it! Let me know if you have any further questions.

Related benchmarks:

Object.assign vs spread v2 (version: 0)

Comparing performance of: Spread vs Object.assign

Created: 7 years ago by: Guest

Jump to the latest result

Spread

Object.assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):