Benchmark: Object copy loop compare

Script Preparation code:

const hasOwnProperty = Object.prototype.hasOwnProperty
function has (obj, key) { return hasOwnProperty.call(obj, key) }
const count = 10000
function loop (fn) { for (let i = count; i > 0; i--) fn() }
var obj = { a: 1, b: 1, c: 1, d: 1, e: 1, f: 1, g: 1 }
var result = {}

Tests:

for-in
loop(function () { for (const key in obj) { if (has(obj, key)) result[key] = obj[key] } })
Object.keys.forEach
loop(function () { Object.keys(obj).forEach(function (key) { result[key] = obj[key] }) })
Object.entries.forEach
loop(function () { Object.entries(obj).forEach(function ([key, value]) { result[key] = value }) })
Object.keys for
loop(function () { const keys = Object.keys(obj) const length = keys.length for (let i = length; i > 0; i--) { const key = keys[i] result[key] = obj[key] } })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in
Object.keys.forEach
Object.entries.forEach
Object.keys for

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

**What is being tested?**

The provided benchmark measures the performance of different ways to copy properties from an object (`obj`) to another object (`result`). The test focuses on four specific approaches:

1. `for-in`
2. `Object.keys.forEach`
3. `Object.entries.forEach`
4. `Object.keys for`

Each approach uses a loop to iterate over the object's properties and assign their values to the result object.

**Options being compared**

The benchmark compares the performance of these four approaches:

* `for-in`: A legacy way to iterate over an object's properties using the `in` operator.
* `Object.keys.forEach`: Uses the `Object.keys()` method to get an array of property names and then iterates over it using the `forEach()` method.
* `Object.entries.forEach`: Uses the `Object.entries()` method to get an array of key-value pairs and then iterates over it using the `forEach()` method.
* `Object.keys for`: A newer way to iterate over an object's properties using a simple `for` loop with the `key` variable.

**Pros and Cons**

Here are some pros and cons for each approach:

1. **for-in**:
	* Pros: Simple and widely supported, can be used in older browsers.
	* Cons: Can be slower due to the use of the `in` operator, which may not be optimized by modern engines.
2. **Object.keys.forEach**:
	* Pros: Modern and efficient, uses a built-in method to get property names.
	* Cons: May not work in older browsers that don't support `Object.keys()`.
3. **Object.entries forEach**:
	* Pros: Efficient and modern, uses a built-in method to get key-value pairs.
	* Cons: May require newer JavaScript engines or polyfills for older browsers.
4. **Object.keys for**:
	* Pros: Newer and efficient, uses a simple `for` loop with a variable.
	* Cons: Not as widely supported as the other approaches (only introduced in ECMAScript 2019).

**Libraries used**

The benchmark defines two custom functions:

1. `hasOwnProperty`: A function that checks if an object has a property with the given name, using the `Object.prototype.hasOwnProperty()` method.
2. `loop`: A function that takes another function as an argument and executes it repeatedly.

**Special JS features or syntax**

None of the individual test cases use any special JavaScript features or syntax beyond the standard ECMAScript 2015 features.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.2 Safari/605.1.15

Browser/OS: Safari 14 on Mac OS X 10.15.6

View result in a separate tab

Test name	Executions per second
for-in	31.5 Ops/sec
Object.keys.forEach	47.9 Ops/sec
Object.entries.forEach	51.5 Ops/sec
Object.keys for	47.6 Ops/sec

Related benchmarks:

Object copy loop compare (version: 3)

Comparing performance of: for-in vs Object.keys.forEach vs Object.entries.forEach vs Object.keys for

Created: 3 years ago by: Registered User

Jump to the latest result

for-in

Object.keys.forEach

Object.entries.forEach

Object.keys for

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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