Benchmark: for let vs Object.keys 2

Script Preparation code:

var myObject = {};
var sum = 0;

for (let i = 0; i < 1000; i++)
    myObject["property_" + Math.random()] = Math.random();

var keys = Object.keys(myObject);

Tests:

for let i in
for (let i in myObject) sum += myObject[i];
Object.keys (cached)
for (let i = 0 ; i < keys.length ; i++) sum += myObject[keys[i]];
Object.keys
const newKeys = Object.keys (myObject); for (let i = 0 ; i < newKeys.length ; i++) sum += myObject[newKeys[i]];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for let i in
Object.keys (cached)
Object.keys

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36

Browser/OS: Chrome 125 on Windows

View result in a separate tab

Object.keys

6K/s

for let i in

6K/s

Object.keys (cached)

5K/s

View exact numbers

Test name	Executions per second
✓ Object.keys	6,167 Ops/sec
for let i in	6,014 Ops/sec
Object.keys (cached)	4,784 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 JavaScript microbenchmark on MeasureThat.net.

The provided benchmark compares three approaches to iterate over an object in JavaScript:

1. **For-in loop**: The first approach uses a traditional `for` loop with `in` keyword, which iterates over the object's own enumerable properties.
```javascript
for (let i in myObject) {
    sum += myObject[i];
}
```
Pros: Simple and straightforward.

Cons: Can be slow for large objects, as it uses a lot of overhead to iterate over the object's properties. Additionally, it can also include non-enumerable properties, which might not be what you want.

2. **Array iteration**: The second approach uses an array of the object's keys, accessed through `Object.keys()` or a cached version.
```javascript
const newKeys = Object.keys(myObject);
for (let i = 0; i < newKeys.length; i++) {
    sum += myObject[newKeys[i]];
}
```
Pros: Faster than the for-in loop, especially for large objects. This is because array iteration is more efficient and doesn't include non-enumerable properties.

Cons: Requires an additional step to get the array of keys, which can add overhead.

3. **Cached Object.keys()**: The third approach uses a cached version of `Object.keys()` that returns a temporary array, rather than creating a new one each time.
```javascript
const newKeys = Object.keys(myObject);
for (let i = 0; i < newKeys.length; i++) {
    sum += myObject[newKeys[i]];
}
```
Pros: Similar to the second approach, but with less overhead since the cache is reused.

Cons: Requires a temporary array allocation, which can add some overhead.

Now, let's look at the specific libraries used in this benchmark:

* None. This benchmark only uses built-in JavaScript features and doesn't rely on any external libraries.

As for special JavaScript features or syntax, the benchmark uses:

* **Template literals**: Used in the `for-in` loop to create a string with dynamic property names.
* **Arrow functions**: Not used explicitly, but implicitly through the use of `const newKeys = Object.keys(myObject);`.

Other alternatives that could be considered for this benchmark include:

* Using `for...of` loop instead of `for...in`, which is a more modern and efficient way to iterate over arrays.
* Using `map()` or `reduce()` methods, which can provide a more concise and expressive way to perform operations on arrays.
* Using a library like Lodash, which provides utility functions for working with objects and arrays.

However, the choice of iteration method ultimately depends on the specific requirements and constraints of the project.

for let vs Object.keys 2 (version: 0)

Comparing performance of: `for let i in vs Object.keys (cached) vs Object.keys`

Created: 2 years ago by: Guest

Go to the latest result

for let i in

Object.keys (cached)

Object.keys

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

for let vs Object.keys 2 (version: 0)

Comparing performance of: for let i in vs Object.keys (cached) vs Object.keys

Created: 2 years ago by: Guest

Go to the latest result

for let i in

Object.keys (cached)

Object.keys

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `for let i in vs Object.keys (cached) vs Object.keys`