Benchmark: Object.assign vs mutate

Script Preparation code:

var numbers = [1,2,3,4,5,6,7,8,9,10];

Tests:

Object.assign
numbers.reduce((obj, i) => Object.assign({}, obj, {i}), {});
Mutate
numbers.reduce((obj, i) => { obj[i] = i; return obj; }, {});

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.assign
Mutate

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36

Browser/OS: Chrome 117 on Windows

View result in a separate tab

Test name	Executions per second
Object.assign	643735.1 Ops/sec
Mutate	4014050.5 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

**What is being tested?**

The provided JSON represents a JavaScript microbenchmark test case, specifically comparing two approaches to achieve the same result: using `Object.assign` and mutating an object directly.

In the first test case, "Mutate", the code uses the `reduce()` method with a callback function that iterates over the array of numbers, assigning each number to an existing property on the accumulator object (`obj`). The goal is to create a new object with all numbers from 1 to 10 as properties.

In the second test case, "Object.assign", the code uses the `reduce()` method with a callback function that creates a new object using `Object.assign()`, passing the accumulator object and an object literal containing each number as a property. The goal is to create a new object with all numbers from 1 to 10 as properties.

**Options being compared**

The two options being compared are:

1. **Mutate**: Directly mutating an object in place using the `reduce()` method.
2. **Object.assign**: Creating a new object by passing an accumulator object and an object literal containing each number as a property using the `reduce()` method.

**Pros and Cons of each approach**

* **Mutate**:
	+ Pros: Typically faster, since no extra object creation is required.
	+ Cons: Might be less readable or maintainable due to potential side effects on the original object.
* **Object.assign**:
	+ Pros: More explicit and readable code, as it creates a new object without modifying an existing one.
	+ Cons: Slower than mutate due to extra object creation.

**Considerations**

When choosing between these approaches, consider the trade-offs between performance and maintainability. If readability is more important, `Object.assign` might be the better choice. However, if speed is critical, mutating the object directly (like in "Mutate") could be faster.

**Library/Features used**

No specific JavaScript libraries are mentioned in this benchmark definition or test cases. No special features or syntax are being tested either. This benchmark focuses solely on the performance comparison between two approaches to achieve a similar result.

**Alternatives**

If you wanted to add more complexity to the benchmark, some alternative test cases could involve:

* Using different methods for object creation (e.g., `Array.prototype.reduce()` vs `Object.create()`).
* Testing with arrays of varying sizes.
* Comparing the performance of other approaches, such as using `Map` or `WeakMap` instead of objects.

However, the current benchmark definition focuses on the fundamental trade-off between mutating an object directly and creating a new object using `Object.assign()`.

Related benchmarks:

Object.assign vs mutate (version: 0)

Comparing performance of: Object.assign vs Mutate

Created: 8 years ago by: Guest

Jump to the latest result

Object.assign

Mutate

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):