Benchmark: slice vs do while

Script Preparation code:

var data = Array(1000).fill(0).map((v, i) => i);

Tests:

slice
var copy = data.slice(0, 100); copy.forEach((v) => console.log(copy));
do while
var i = 0; do { console.log(data[i]); i++; } while(i < 100)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
do while

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
slice	510.4 Ops/sec
do while	4790.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain what's being tested in this JavaScript microbenchmark.

**Overview**

The benchmark is comparing two approaches to iterate over an array: `slice()` and `do-while` loops. The goal is to determine which approach is faster.

**Options Compared**

There are only two options being compared:

1. **`slice()`**: This method creates a new array that contains a subset of the elements from the original array. In this case, we're creating an array with 1000 elements and then using `slice(0, 100)` to extract the first 100 elements.
2. **`do-while` loop**: This type of loop is similar to a traditional `for` loop but has a different initialization and termination condition.

**Pros and Cons**

1. **`slice()`**:
	* Pros: Creates a new array, which can be beneficial for certain use cases (e.g., when working with large datasets).
	* Cons: Allocates additional memory for the new array, which can lead to slower performance if the original array is already large.
2. **`do-while` loop**:
	* Pros: Can be more efficient than `slice()` since it doesn't allocate new memory.
	* Cons: Requires manual index management and can be less readable for some developers.

**Library Used**

There is no explicit library mentioned in the benchmark definition or test cases, but we can infer that the benchmark is using a JavaScript engine like V8 (used by Chrome) to execute the tests. The `RawUAString` field in the latest benchmark result suggests that the results are reported in UAParser format, which is used to identify and report details about user agents.

**Special JS Feature or Syntax**

There are no special JS features or syntax mentioned in the test cases or benchmark definition.

**Benchmark Preparation Code**

The preparation code for each test case sets up an array `data` with 1000 elements and then calls one of the two approaches being compared:

1. For the `slice()` test, it creates a new array using `slice(0, 100)` and then iterates over the first 100 elements.
2. For the `do-while` test, it initializes an index variable `i` to 0 and then enters a loop that increments `i` until it reaches 100.

**Other Alternatives**

If you're interested in exploring alternative approaches to iterate over arrays, here are a few examples:

1. **`forEach()`**: This method is a more modern way to iterate over an array and doesn't require manual index management.
2. **`map()` + `forEach()`**: Combining `map()` (which applies a callback function to each element) with `forEach()` can provide a good balance between readability and performance.
3. **Closures or higher-order functions**: Using closures or higher-order functions like `reduce()` or `every()` can also be effective ways to iterate over arrays.

Keep in mind that the choice of iteration approach depends on the specific use case, performance requirements, and personal preference.

Related benchmarks:

slice vs do while (version: 0)

Comparing performance of: slice vs do while

Created: 2 years ago by: Guest

Jump to the latest result

slice

do while

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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