Benchmark: js Count the occurences of an item in an array

Tests:

arr.filter
count = function(arr, item) { return arr.filter(function(x){return x==item}).length } count([1,2,3,2,4,2], 2);
for
count = function(arr, item) { var count = 0; for(var i = 0; i < arr.length; ++i){ if(arr[i] == item) count++; } return count } count([1,2,3,2,4,2], 2);
arr.reduce
count = function(arr, item) { return arr.reduce(function(total,x){return x==item ? total+1 : total}, 0); } count([1,2,3,2,4,2], 2);
regex
count = function(arr, item) { var regex = new RegExp('[^'+item+']+', 'g'); return String(arr).replace(regex,'').length } count([1,2,3,2,4,2], 3);
indexOf
count = function(arr, item) { var count= 0, i; while((i= arr.indexOf(item, i))!= -1){ ++count; ++i; } return count; } count([1,2,3,2,4,2], 2);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
arr.filter
for
arr.reduce
regex
indexOf

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
arr.filter	10780288.0 Ops/sec
for	11988019.0 Ops/sec
arr.reduce	12155319.0 Ops/sec
regex	2858277.5 Ops/sec
indexOf	9523024.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The benchmark definition provides a brief description of what is being measured: counting the occurrences of an item in an array. The script preparation code and HTML preparation code are empty, indicating that these steps do not need to be executed before running the benchmarks.

**Individual Test Cases**

There are four test cases:

1. **arr.filter**: This test case uses the `filter()` method to create a new array with only the elements that pass the test implemented by the provided function.
2. **for**: This test case uses a traditional `for` loop to iterate through the array and count the occurrences of the item.
3. **arr.reduce**: This test case uses the `reduce()` method to apply a binary function (in this case, incrementing a counter) to an accumulator value (the current element being processed) across all elements in the array.
4. **regex**: This test case uses regular expressions to search for the item in the string representation of the array and count the matches.
5. **indexOf**: This test case uses the `indexOf()` method to find the index of the first occurrence of the item in the array, then increments a counter for each subsequent match.

**Options Compared**

Each test case is comparing a different approach to counting occurrences:

* `arr.filter` vs. `for`: The `filter()` method is often faster than a traditional `for` loop because it avoids the overhead of incrementing a counter.
* `arr.reduce` vs. `for`: The `reduce()` method can be more efficient than a traditional `for` loop because it allows for accumulation and iteration in a single pass.
* `regex` vs. `indexOf`: Regular expressions are often slower than using `indexOf()` because they require the browser's regex engine to execute.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* **arr.filter**: Pros: fast, efficient; Cons: requires creating a new array, can be slow for large inputs.
* **for**: Pros: straightforward, easy to understand; Cons: slow due to counter incrementation.
* **arr.reduce**: Pros: efficient accumulation, single pass through the array; Cons: may require more complex implementation.
* **regex**: Pros: flexible pattern matching; Cons: slow due to regex engine overhead.
* **indexOf**: Pros: fast, efficient; Cons: limited to finding a single match.

**Library Usage**

None of the test cases use an external library (e.g., jQuery).

**Special JS Features or Syntax**

None of the test cases employ special JavaScript features or syntax (e.g., `let`, `const`, arrow functions). However, some might use modern JavaScript features not supported in older browsers.

**Alternatives**

Some alternative approaches to counting occurrences could be:

* Using an array-based solution with a single pass through the array.
* Utilizing native browser methods like `Array.prototype.some()` or `Array.prototype.every()`.
* Leveraging external libraries like Lodash or Underscore.js for more efficient filtering and mapping.

Keep in mind that each approach has its strengths and weaknesses, and the best choice depends on specific requirements and performance constraints.

Related benchmarks:

js Count the occurences of an item in an array (version: 6)

Comparing performance of: arr.filter vs for vs arr.reduce vs regex vs indexOf

Created: 8 years ago by: Registered User

Jump to the latest result

arr.filter

for

arr.reduce

regex

indexOf

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):