Benchmark: entries vs for vs foreach vs some vs every

Script Preparation code:

function makeid() {
  var text = "";
  var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

  for (var i = 0; i < 5; i++)
    text += possible.charAt(Math.floor(Math.random() * possible.length));

  return text;
}

window.parentArr = [];

for (let i = 0; i < 100; i++) {
	window.parentArr.push(makeid());
}

Tests:

entries
const newObj = {}; for (const [i, v] of window.parentArr.entries()) { if ((i % 2) === 0) { newObj[i] = v; } }
for
const newObj = {}; for (let i = 0; i < window.parentArr.length; i++) { if ((i % 2) === 0) { newObj[i] = window.parentArr[i]; } }
foreach
const newObj = {}; window.parentArr.forEach((v, i) => { if ((i % 2) === 0) { newObj[i] = v; } })
some
const newObj = {}; window.parentArr.some((v, i) => { if ((i % 2) === 0) { newObj[i] = v; } return false; })
every
const newObj = {}; window.parentArr.every((v, i) => { if ((i % 2) === 0) { newObj[i] = v; } return true; })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
entries
for
foreach
some
every

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/115.0.0.0 Safari/537.36

Browser/OS: Chrome 115 on Windows

View result in a separate tab

Test name	Executions per second
entries	339271.6 Ops/sec
for	29325.1 Ops/sec
foreach	597317.2 Ops/sec
some	614463.9 Ops/sec
every	601858.6 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Overview**

The provided benchmark measures the performance of four different approaches to iterate over an array in JavaScript:

1. `entries`
2. `for` loop
3. `forEach`
4. `some` (and implicitly, `every`, although the latter is not explicitly included in the test)

Each approach is used to filter the elements of an array and create a new object with only every other element.

**Options compared**

The benchmark compares the performance of these four approaches:

1. `entries`: Uses the `entries()` method of the array, which returns an iterator over the keys of the array.
2. `for` loop: Uses a traditional `for` loop to iterate over the indices of the array.
3. `forEach`: Uses the `forEach()` method, which executes a callback function for each element in the array.
4. `some` (and implicitly, `every`): Uses the `some()` and `every()` methods, respectively, to check if at least one or all elements of the array satisfy a certain condition.

**Pros and cons**

Here are some pros and cons of each approach:

1. **entries**:
	* Pros: Efficient use of iterator protocol, avoids unnecessary array indexing.
	* Cons: May be slower than traditional `for` loop due to iterator overhead.
2. **for** loop:
	* Pros: Fast and efficient for small arrays.
	* Cons: May require more memory allocation if the array is large.
3. **forEach**:
	* Pros: Convenient and concise syntax.
	* Cons: May be slower than traditional `for` loop or `entries` due to callback function overhead.
4. **some** and **every**:
	* Pros: Efficient use of built-in methods, avoids unnecessary array indexing.
	* Cons: May not be suitable for all use cases (e.g., when the condition depends on the value, not just its index).

**Library and special JS feature**

None of the benchmarked approaches rely on a specific library or a special JavaScript feature.

**Other alternatives**

If you need to iterate over an array in JavaScript, here are some other alternatives:

* `map()`: Creates a new array with the results of applying a given function to each element.
* `reduce()`: Applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.
* `filter()`: Creates a new array with all elements that pass the test implemented by the provided function.

These alternatives can be used for different purposes, such as creating a new array, accumulating values, or filtering out elements. However, they may not always offer the same performance benefits as the benchmarked approaches.

Related benchmarks:

entries vs for vs foreach vs some vs every (version: 0)

Comparing performance of: entries vs for vs foreach vs some vs every

Created: one year ago by: Guest

Jump to the latest result

entries

for

foreach

some

every

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):