Benchmark: Object.entries vs for..in

Script Preparation code:

var obj = {
	a: 1,
    b: 2,
	c: 3,
	d: 4,
	0: 'a',
  	1: 'b',
  	str: 'long string',
	nested: {
    	nested: 0
    },
	hello: 55.5
};
for (let i = 10; i < 10000; i++) { obj[""+i] = "test" }

Tests:

Object.entries (forEach)
Object.entries(obj).forEach((key, value) => console.log(key, value));
for..in
for (let key in obj) { if (obj.hasOwnProperty(key)) console.log(key, obj[key]); }
Object.entries (for loop)
for (let entries = Object.entries(obj), i = entries.length - 1, entry = entries[i]; i >= 0; entry = entries[i--]) { console.log(entry[0], entry[1]) }

Historical Performance Data aggregated from 21 community runs

Desktop Results:

Chrome 13 runs

Object.entries (for loop)

24/s

Object.entries (forEach)

22/s

for..in

21/s

Fastest: Object.entries (for loop) (1.2x faster)

View exact numbers

✓ Object.entries (for loop): 24 ops/sec
• Object.entries (forEach): 22 ops/sec
• for..in: 21 ops/sec

Firefox 8 runs

for..in

28/s

Object.entries (forEach)

27/s

Object.entries (for loop)

27/s

View exact numbers

✓ for..in: 28 ops/sec
• Object.entries (forEach): 27 ops/sec
• Object.entries (for loop): 27 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.entries (forEach)
for..in
Object.entries (for loop)

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:152.0) Gecko/20100101 Firefox/152.0

Browser/OS: Firefox 152 on Linux

View result in a separate tab

for..in

29/s

Object.entries (for loop)

29/s

Object.entries (forEach)

28/s

View exact numbers

Test name	Executions per second
✓ for..in	29 Ops/sec
Object.entries (for loop)	29 Ops/sec
Object.entries (forEach)	28 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation.

The provided JSON represents a JavaScript benchmark test case, specifically comparing three approaches to iterate over an object:

1.  `Object.entries(obj).forEach((key, value) => console.log(key, value));`
2.  `for (let key in obj) { if (obj.hasOwnProperty(key)) console.log(key, obj[key]); }`
3.  `for (let entries = Object.entries(obj), i = entries.length - 1, entry = entries[i]; i >= 0; entry = entries[i--]) { console.log(entry[0], entry[1]) }`

**Option Comparison:**

*   **`Object.entries()` with `forEach`**: This approach uses the `Object.entries()` method to get an array of key-value pairs and then uses the `forEach` method to iterate over each pair. The `forEach` method executes a provided callback function once for each element in the array.
*   **`for...in` loop**: This traditional loop iterates over the object's property names, checking if each property is an own property of the object using `obj.hasOwnProperty(key)`. It logs the key and its corresponding value to the console.
*   **`Object.entries()` with manual for loop**: This approach uses the same `Object.entries()` method as before but then manually iterates over the array of key-value pairs in a loop. It logs each key-value pair to the console.

**Pros and Cons:**

*   **`Object.entries()` with `forEach`:**
    *   Pros:
        *   More concise and readable code.
        *   No need to check if property is an own property using `obj.hasOwnProperty(key)`.
    *   Cons:
        *   Requires JavaScript version 16 or higher for `forEach` method on array literals.
*   **`for...in` loop:**
    *   Pros:
        *   Works across all supported JavaScript versions and environments.
        *   No need to require additional libraries or modules.
    *   Cons:
        *   Less concise and readable code compared to other approaches.
        *   Requires explicit checking for own properties using `obj.hasOwnProperty(key)`.
*   **`Object.entries()` with manual for loop:**
    *   Pros:
        *   Offers more control over the iteration process, allowing for fine-tuning of performance optimization techniques.
        *   Works across all supported JavaScript versions and environments.
    *   Cons:
        *   Less concise and readable code compared to other approaches.

**Library Usage:**

None of the provided test cases use any external libraries or modules. The `Object.entries()` method is a built-in method in JavaScript, and the `for...in` loop is also a native JavaScript construct.

**Special JS Features/Syntax:**

The provided test case does not include any special features or syntax that require specific versions of JavaScript or specialized tools.

**Alternatives:**

If you need to benchmark different approaches for iterating over objects, here are some alternatives:

*   **Use the built-in `for...in` loop**: As mentioned earlier, this is a traditional loop that iterates over object property names.
*   **Utilize modern methods like `Object.keys()` and `Array.prototype.forEach()`**: These methods provide more concise and readable ways to iterate over objects, but may require specific JavaScript versions or environments.
*   **Use specialized libraries or frameworks for performance benchmarking**: If you need highly optimized benchmarks with fine-grained control, consider using specialized libraries or frameworks designed for performance benchmarking.

Object.entries vs for..in (version: 0) Benchmark.js

Comparing performance of: `Object.entries (forEach) vs for..in vs Object.entries (for loop)`

Created: 2 years ago by: Guest

Go to the latest result

Object.entries (forEach)

for..in

Object.entries (for loop)

Historical Performance Data aggregated from 21 community runs

Desktop Results:

Chrome 13 runs

Firefox 8 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Object.entries vs for..in (version: 0) Benchmark.js

Comparing performance of: Object.entries (forEach) vs for..in vs Object.entries (for loop)

Created: 2 years ago by: Guest

Go to the latest result

Object.entries (forEach)

for..in

Object.entries (for loop)

Historical Performance Data aggregated from 21 community runs

Desktop Results:

Chrome 13 runs

Firefox 8 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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Comparing performance of: `Object.entries (forEach) vs for..in vs Object.entries (for loop)`