Benchmark: variety of loops in js

Script Preparation code:

   var arr = [];
    for (var i = 0; i < 1000; i++) {
      arr[i] = i;
    }
  
    function someFn(i) {
      return i * 3 * 8;
    }

Tests:

foreach
arr.forEach(function (item){ someFn(item); })
for++
for (var i = 0, len = arr.length; i < len; i++) { someFn(arr[i]); }
map
arr.map(item => someFn(item))
for of
for (var value of arr) { someFn(value); }
for in
for (var i in arr) { someFn(arr[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for++
map
for of
for in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36

Browser/OS: Chrome 83 on Windows

View result in a separate tab

Test name	Executions per second
foreach	7927.8 Ops/sec
for++	4437.1 Ops/sec
map	7243.0 Ops/sec
for of	7461.5 Ops/sec
for in	3695.9 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll dive into explaining the JavaScript microbenchmark you provided.

**Benchmark Definition**

The benchmark definition is represented by two code snippets:

1. **Script Preparation Code**: This code initializes an array `arr` with 1000 elements, each containing its index value (e.g., `0`, `1`, ..., `999`). It also defines a simple function `someFn(i)` that takes an integer `i` as input and returns the result of `i * 3 * 8`. This function is used in various test cases.
2. **Html Preparation Code**: This field is empty, indicating that no HTML code is needed for this benchmark.

**Test Cases**

The benchmark consists of five individual test cases:

1. **foreach**
	* Benchmark Definition: `arr.forEach(function (item){\r\n  someFn(item);\r\n})`
	* Purpose: This test case measures the performance of iterating over an array using the `forEach()` method.
2. **for++**
	* Benchmark Definition: `for (var i = 0, len = arr.length; i < len; i++) {\r\n  someFn(arr[i]);\r\n}`
	* Purpose: This test case measures the performance of iterating over an array using a traditional `for` loop with incrementing index.
3. **map**
	* Benchmark Definition: `arr.map(item => someFn(item))`
	* Purpose: This test case measures the performance of mapping an array using the `map()` method.
4. **for of**
	* Benchmark Definition: `for (var value of arr) {\r\n  someFn(value);\r\n}`
	* Purpose: This test case measures the performance of iterating over an array using a `for...of` loop.
5. **for in**
	* Benchmark Definition: `for (var i in arr) {\r\n  someFn(arr[i]);\r\n}`
	* Purpose: This test case measures the performance of iterating over an array using a traditional `for` loop with the `in` operator.

**Options Compared**

The benchmark compares the performance of five different iteration approaches:

1. **forEach()**: Iterating over an array using the `forEach()` method.
2. **Traditional for loop (++i)**: Iterating over an array using a traditional `for` loop with incrementing index.
3. **map()**: Mapping an array using the `map()` method, which also returns a new array.
4. **For...of loop**: Iterating over an array using a `for...of` loop, which is more concise and readable.
5. **Traditional for loop (i in)**: Iterating over an array using a traditional `for` loop with the `in` operator.

**Pros and Cons**

Here's a brief summary of each approach:

1. **forEach()**: Pros: concise, easy to read, and doesn't modify the original array.
	* Cons: may be slower due to the function invocation overhead.
2. **Traditional for loop (++i)**: Pros: well-known, efficient, and can be used with arrays and objects.
	* Cons: more verbose, prone to errors, and not as concise as `forEach()` or `for...of`.
3. **map()**: Pros: concise, efficient, and returns a new array.
	* Cons: may incur additional overhead due to the creation of a new array.
4. **For...of loop**: Pros: concise, easy to read, and doesn't modify the original array.
	* Cons: not as well-known as traditional `for` loops or `forEach()`.
5. **Traditional for loop (i in)**: Pros: well-known, efficient, and can be used with arrays and objects.
	* Cons: more verbose, prone to errors, and not as concise as `forEach()` or `for...of`.

**Other Considerations**

1. **Array iteration**: When iterating over an array, the engine needs to perform a bounds check on the length of the array. This can introduce overhead if the array is large.
2. **Function invocation overhead**: In some cases, the engine may need to invoke a function for each element in the array (e.g., `forEach()`). This can incur additional overhead.

**Alternatives**

Other alternatives for iterating over arrays include:

1. **Array.prototype.every()**: Similar to `forEach()`, but returns a boolean value indicating whether all elements pass the test.
2. **Array.prototype.some()**: Similar to `forEach()`, but returns a boolean value indicating whether at least one element passes the test.
3. **For...of loop with a custom callback function**: Allows for more control over the iteration process.

Keep in mind that these alternatives may have different performance characteristics or use cases, so it's essential to choose the right approach depending on your specific needs.

Related benchmarks:

variety of loops in js (version: 0)

Comparing performance of: foreach vs for++ vs map vs for of vs for in

Created: 5 years ago by: Guest

Jump to the latest result

foreach

for++

map

for of

for in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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