Benchmark: Object creation: reduce vs. for

Script Preparation code:

var a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

Tests:

reduce
return a.reduce((acc, item) => { acc[item] = undefined; return acc; }, {});
for loop
const out = {}; for(let i = 0; i < a.length; i++) { out[a[i]] = undefined; } return out;
forEach loop
const out = {}; a.forEach((key) => { out[key] = undefined; }) return out;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reduce
for loop
forEach loop

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Fedora; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36

Browser/OS: Chrome 90 on Fedora

View result in a separate tab

Test name	Executions per second
reduce	526035.8 Ops/sec
for loop	307263.8 Ops/sec
forEach loop	498653.7 Ops/sec

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

LLMs can make mistakes. Check important info.

Measuring the performance of different JavaScript approaches is crucial in understanding how the language executes and can be optimized.

The provided benchmark compares three approaches to create an object with keys from an array: reducing, using a for loop, and using the `forEach` method.

**Approaches Compared:**

1.  **Reduce Method (`reduce()`)**: The reduce method applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single output value.
2.  **For Loop**: This approach involves iterating over the array using a for loop, adding elements from the array as keys to the object, and setting their values to undefined.

**Pros and Cons of Each Approach:**

1.  **Reduce Method (`reduce()`)**

*   Pros:

*   Often more concise and readable.
        *   Can be more memory-efficient since it doesn't create intermediate objects or arrays.
        *   Suitable for tasks that involve reducing multiple data structures to a single output value.
    *   Cons:

*   It might not be as straightforward to understand, especially for developers unfamiliar with the reduce method.
        *   In some cases, its performance can vary based on the specific implementation details of the browser's JavaScript engine.

2.  **For Loop**

*   Pros:

*   More intuitive and easier to understand, especially for those familiar with traditional loops.
        *   Can be more readable when handling complex logic or conditional statements within the loop body.
        *   Suitable for situations where memory efficiency isn't a top priority.
    *   Cons:

*   It might not always result in more memory-efficient code due to the creation of intermediate variables or arrays.
        *   The code can become more verbose and less readable as the number of elements increases.

**Library Used (if applicable):**

None

In this benchmark, no specific libraries are used. However, some browsers may use their own optimizations or extensions for these built-in methods that could affect performance under certain conditions.

**Special JS Feature/Syntax:**

None mentioned explicitly in this benchmark but is worth noting generally:

*   Modern JavaScript includes features such as async/await and promises, which can significantly impact performance depending on how they are used.
*   The spread operator (`{...}`) and destructuring syntax (e.g., `const [key1, key2] = objectKeys`) are also powerful tools for creating objects but may be less commonly seen in benchmarks focused strictly on array manipulation.

**Alternative Approaches:**

While the provided benchmark specifically compares reduce, for loop, and forEach methods, other approaches might include:

*   Using object literal syntax with destructuring (`const out = { [a[i]]: undefined };`)
*   Utilizing `Map` objects instead of plain objects for key-value pairs.
*   Employing more advanced techniques like `Map.prototype.set()` or `Promise.all()` to create and manipulate arrays.

These alternatives can provide different trade-offs in terms of performance, memory usage, code readability, and complexity.

Related benchmarks:

Object creation: reduce vs. for (version: 0)

Comparing performance of: reduce vs for loop vs forEach loop

Created: 3 years ago by: Registered User

Jump to the latest result

reduce

for loop

forEach loop

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):