Benchmark: map vs reduce - MeasureThat.net

Script Preparation code:

function generateTestArray() {
    const result = [];
    for (let i = 0; i < 10000; ++i) {
        result.push(i);
    }
    return result;
}

Tests:

map
const testArray = generateTestArray() testArray.map(i => { i })
reduce
const testArray = generateTestArray() testArray.reduce((acc, i) => [...acc, { i }], [])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
map
reduce

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

Browser/OS: Chrome 108 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
map	10376.9 Ops/sec
reduce	14.9 Ops/sec

Autogenerated LLM Summary (model llama3.1:latest, generated 2 months ago):

LLMs can make mistakes. Check important info.

Let's dive into what is being tested here.

**Benchmark Name:** `map vs reduce`

This benchmark compares the performance of two different methods in JavaScript: `Array.prototype.map()` and `Array.prototype.reduce()`. Both methods are used to transform or accumulate values in an array, but they have distinct approaches.

**Test Case 1: `map`**

The first test case uses the `map()` method:
```javascript
const testArray = generateTestArray()
testArray.map(i => { i })
```
In this example, the `map()` method is used to create a new array with the same elements as the original array (`testArray`). The callback function `{ i }` simply returns the current element `i` without modifying it. This test case measures how long it takes to execute the `map()` operation.

**Test Case 2: `reduce`**

The second test case uses the `reduce()` method:
```javascript
const testArray = generateTestArray()
testArray.reduce((acc, i) => [...acc, { i }], [])
```
Here, the `reduce()` method is used to accumulate a new array with the same elements as the original array (`testArray`). The callback function `(acc, i) => [...acc, { i }]` takes two arguments: `acc` (the accumulated value, initialized to an empty array `[]`) and `i` (the current element). It returns a new array by spreading the accumulated value (`acc`) and adding a new object with property `i`. This test case measures how long it takes to execute the `reduce()` operation.

**Library:** None

No external libraries are used in these test cases. The `generateTestArray` function is a custom implementation that creates an array of 10,000 elements for testing purposes.

**JS Feature or Syntax:** None

No special JavaScript features or syntax are used in these test cases.

Now, let's discuss the pros and cons of using `map()` vs `reduce()`:

### Map()

Pros:

1. **Efficient**: `map()` is generally faster than `reduce()`, as it doesn't require accumulating values.
2. **Simple**: The callback function for `map()` is typically simpler to write, as you only need to process each element once.

Cons:

1. **Memory usage**: If the resulting array is large, using `map()` can create a new array with the same size, which may lead to memory issues.

### Reduce()

Pros:

1. **Accumulation**: `reduce()` allows for efficient accumulation of values, making it suitable for operations like summing or concatenating.
2. **Flexibility**: The callback function for `reduce()` can take two arguments (acc and current element), giving you more control over the processing logic.

Cons:

1. **Complexity**: Writing a correct `reduce()` implementation can be challenging, especially when dealing with nested arrays or complex data structures.
2. **Performance**: `reduce()` might be slower than `map()`, as it involves accumulating values.

Alternatives to consider:

* For simple transformations, you can use `Array.prototype.forEach()` instead of `map()` or `reduce()`.
* If you need to perform more complex operations, look into using libraries like Lodash or Underscore.js, which provide higher-order functions for array manipulation.
* In some cases, a plain loop might be the most efficient solution.

That's it! I hope this explanation helped you understand what is being tested in these benchmark tests.

Related benchmarks:

map vs reduce (version: 0)

Comparing performance of: map vs reduce

Created: one year ago by: Guest

Jump to the latest result

map

reduce

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated 2 months ago):