Benchmark: JavaScript Object.assign vs for in loop (-2)

Tests:

Object.assign
const a = { x: 'xxx', y: 1, z: null } const b = { z: 1, u: 'uuu', v: { a: 9 } } Object.assign(a, b); Object.assign(b, a);
for in loop
const a = { x: 'xxx', y: 1, z: null } const b = { z: 1, u: 'uuu', v: { a: 9 } } for (let prop in b) a[prop] = b[prop]; for (let prop in a) b[prop] = a[prop];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.assign
for in loop

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; rv:129.0) Gecko/20100101 Firefox/129.0

Browser/OS: Firefox 129 on Windows

View result in a separate tab

Test name	Executions per second
Object.assign	7525939.5 Ops/sec
for in loop	7515853.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

**What is being tested?**

The provided benchmark tests two approaches for copying objects: `Object.assign` and a manual `for in loop` approach.

**Options compared:**

1. **Object.assign**: This method uses the spread operator (`{...obj}`) to create a new object, and then assigns properties from one object to another.
2. **Manual for in loop**: This approach iterates over the properties of an object using a `for in` loop, assigning values from one object to another.

**Pros and Cons:**

1. **Object.assign**:
	* Pros:
		+ Concise and readable
		+ Efficient, as it creates a new object with a shallow copy of properties
	* Cons:
		+ May be slower than the manual `for in loop` approach for very large objects or deep copying
2. **Manual for in loop**:
	* Pros:
		+ Can be faster for large objects or deep copying, as it avoids creating a new object and only copies properties on-the-fly
	* Cons:
		+ Less readable and maintainable due to the need to manage property iteration manually

**Library/Functionality used:**

1. `Object.assign`: This is a built-in JavaScript method for assigning properties from one object to another.

**Special JS feature/syntax:**

None mentioned in this benchmark.

**Other considerations:**

* The manual `for in loop` approach may be more suitable for certain use cases, such as when dealing with large objects or deep copying.
* The `Object.assign` method is generally considered more readable and maintainable, but may not be as efficient for very large objects or deep copying.

**Alternatives:**

1. Other object assignment methods, such as `JSON.parse(JSON.stringify(obj))`, which can also achieve the same result.
2. Library functions like Lodash's `cloneDeep` or `merge`, which provide more comprehensive and flexible object copying solutions.
3. Other JavaScript engines or interpreters that may optimize or have different performance characteristics for these benchmarks.

Note: The choice of approach depends on the specific use case, performance requirements, and personal preference.

Related benchmarks:

JavaScript Object.assign vs for in loop (-2) (version: 0)

Comparing performance of: Object.assign vs for in loop

Created: one year ago by: Guest

Jump to the latest result

Object.assign

for in loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):