Benchmark: for loop vs array map

Tests:

for loop
const numbers = Array(100000).fill(0); for (let i = 0; i < numbers.length; i++) { numbers[i] = i; } const doubled = Array(numbers.length).fill(null); for (let i = 0; i < numbers.length; i++) { doubled[i] = numbers[i] * 2; }
Array.prototype.map
const numbers = Array(100000).fill(0); for (let i = 0; i < numbers.length; i++) { numbers[i] = i; } const doubled = numbers.map((x) => x * 2);
for loop using a sparse array
const numbers = Array(100000).fill(0); for (let i = 0; i < numbers.length; i++) { numbers[i] = i; } const doubled = Array(numbers.length); for (let i = 0; i < numbers.length; i++) { doubled[i] = numbers[i] * 2; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for loop
Array.prototype.map
for loop using a sparse array

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:132.0) Gecko/20100101 Firefox/132.0

Browser/OS: Firefox 132 on Linux

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Test name	Executions per second
for loop	802.8 Ops/sec
Array.prototype.map	684.4 Ops/sec
for loop using a sparse array	876.3 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):

LLMs can make mistakes. Check important info.

The benchmark on MeasureThat.net is testing the performance of different approaches to iterating over an array in JavaScript, specifically comparing a traditional `for` loop, the `Array.prototype.map()` method, and another variation that also uses a `for` loop but works on a sparse array.

### 1. Approaches Being Compared

1. **For Loop**:
    - **Code**: 
      ```javascript
      const numbers = Array(100000).fill(0);
      for (let i = 0; i < numbers.length; i++) {
        numbers[i] = i;
      }
      
      const doubled = Array(numbers.length).fill(null);
      for (let i = 0; i < numbers.length; i++) {
        doubled[i] = numbers[i] * 2;
      }
      ```
    - **Test Name**: For loop
    - **Explanation**: The standard `for` loop manually increments the index, populating the `numbers` array and then doubling each number in the second loop.

2. **Array.prototype.map**:
    - **Code**: 
      ```javascript
      const numbers = Array(100000).fill(0);
      for (let i = 0; i < numbers.length; i++) {
        numbers[i] = i;
      }
      
      const doubled = numbers.map((x) => x * 2);
      ```
    - **Test Name**: Array.prototype.map
    - **Explanation**: This uses the `map` method, which is a more functional programming approach. It applies the doubling operation over the `numbers` array, returning a new array.

3. **For Loop Using Sparse Array**:
    - **Code**: 
      ```javascript
      const numbers = Array(100000).fill(0);
      for (let i = 0; i < numbers.length; i++) {
        numbers[i] = i;
      }
      
      const doubled = Array(numbers.length);
      for (let i = 0; i < numbers.length; i++) {
        doubled[i] = numbers[i] * 2;
      }
      ```
    - **Test Name**: For loop using a sparse array
    - **Explanation**: In this version, the `doubled` array is initialized without filling it with values. Instead, it is directly set during the loop. This approach can be more efficient in terms of memory allocation for some engines.

### 2. Performance Results

- The benchmark results indicate the number of executions per second for each method. The `for loop using a sparse array` is the fastest at approximately **1686.11** executions per second, followed by the `for loop` at **1211.54**, and finally, the `Array.prototype.map` at **810.33**.

### 3. Pros and Cons of Each Approach

- **For Loop**:
    - **Pros**:
        - Generally faster due to optimizations in JavaScript engines.
        - More control over the iteration process.
    - **Cons**:
        - More boilerplate code.
        - Error-prone if not handled correctly (e.g., index out of bounds).

- **Array.prototype.map()**:
    - **Pros**:
        - Cleaner and more readable code.
        - Takes care of the iteration internally, reducing chances of error.
    - **Cons**:
        - Slightly slower, due to the overhead of function calls.
        - Creates a new array, which can have memory implications.

- **For Loop Using Sparse Array**:
    - **Pros**:
        - Can be more memory efficient when initialized properly.
        - May lead to better performance in certain JavaScript engines.
    - **Cons**:
        - Initializing a sparse array might lead to confusion for developers unfamiliar with its behavior.
        - Still requires manual index management.

### 4. Other Considerations

- **Optimization**: JavaScript engines (like V8, which powers Chrome) have different optimization strategies. The performance of these loops might vary based on how the engine interprets the code.
- **Readability vs Performance**: While array methods like `map` are cleaner and often touted for readability, in performance-critical sections of code, developers may opt for traditional loops.
- **Alternative Methods**: 
    - Other alternatives to these iterative techniques include using `forEach()`, which is another method provided by JavaScript for array iteration, or leveraging modern paradigms like asynchronous programming with `async/await` and `Promises`, especially if the operation involves I/O-bound tasks.

These considerations will help software engineers understand the trade-offs involved with each approach, allowing them to choose one that fits their specific needs based on performance requirements as well as code maintainability.

Related benchmarks:

for loop vs array map (version: 1)

Comparing performance of: for loop vs Array.prototype.map vs for loop using a sparse array

Created: one month ago by: Guest

Jump to the latest result

for loop

Array.prototype.map

for loop using a sparse array

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):