Benchmark: compare the ways to generate an array filled with empty objects for iteration

compare the ways to generate an array filled with empty objects for iteration (version: 1)

- Array.push - Array.apply: Array.apply(null, Array(100)) - Destructuring operator: [...Array(100)] - Array.prototype.fill Array(100).fill(undefined) - Array.from Array.from({ length: 100 })

Comparing performance of: Array.apply(null, Array(n)) vs [...Array(n)] vs Array(n).fill(null) vs Array.from({ length: n }) vs Array.from({ length:n }, (item, i) => i) vs Array.push vs Array with length + push

Created: 2 months ago by: Guest

Jump to the latest result

Tests:

Array.apply(null, Array(n))
Array.apply(null, Array(1000)).map((item, i) => {});
[...Array(n)]
[...Array(1000)].map((item, i) => {});
Array(n).fill(null)
Array(1000).fill(null).map((item, i) => {});
Array.from({ length: n })
Array.from({ length: 1000 }).map((item, i) => {});
Array.from({ length:n }, (item, i) => i)
Array.from({ length:1000 }, (item, i) => {});
Array.push
const arr = [] for (let i = 0; i < 1000; ++i) arr.push({})
Array with length + push
const arr = new Array(1000); for (let i = 0; i < 1000; ++i) arr.push({})

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.apply(null, Array(n))
[...Array(n)]
Array(n).fill(null)
Array.from({ length: n })
Array.from({ length:n }, (item, i) => i)
Array.push
Array with length + push

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36

Browser/OS: Chrome 132 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Array.apply(null, Array(n))	245904.2 Ops/sec
[...Array(n)]	375066.8 Ops/sec
Array(n).fill(null)	386268.6 Ops/sec
Array.from({ length: n })	40169.3 Ops/sec
Array.from({ length:n }, (item, i) => i)	34887.6 Ops/sec
Array.push	325620.8 Ops/sec
Array with length + push	262179.2 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 months ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON compares different methods of creating an array filled with empty objects (or a specific value) suitable for iteration in JavaScript. Each method is assessed by measuring how quickly it can perform the operation for an array of size 1,000.

### Comparison of Methods:

1. **Array.push**
   - **Definition**: `const arr = [];\nfor (let i = 0; i < 1000; ++i) arr.push({});`
   - **Pros**: This method is straightforward and commonly used. It allows for dynamic array growth if the number of elements is unknown.
   - **Cons**: This approach is generally slower since it involves multiple resizes and may incur overhead from repeated method calls to `push`.

2. **Array with length + push**
   - **Definition**: `const arr = new Array(1000);\nfor (let i = 0; i < 1000; ++i) arr.push({});`
   - **Pros**: Initializing an array with a specific length can slightly improve performance since the engine can prepare the memory in advance.
   - **Cons**: Similar to the previous method, it still incurs overhead from multiple calls to `push`.

3. **Array.apply**
   - **Definition**: `Array.apply(null, Array(1000)).map((item, i) => {});`
   - **Pros**: This can create an array with a specified length using the `apply` method on `Array`, which can be concise for certain use cases.
   - **Cons**: This approach is typically slower because `apply` has some overhead, and constructing an array this way can introduce complexity.

4. **Spread operator**
   - **Definition**: `[...Array(1000)].map((item, i) => {});`
   - **Pros**: The spread operator provides a clean, modern syntax for array creation and works well with mapping and characterizing elements.
   - **Cons**: Similar to `apply`, the spread operator can be slower in some cases, especially due to generating intermediate objects.

5. **Array.prototype.fill**
   - **Definition**: `Array(1000).fill(null).map((item, i) => {});`
   - **Pros**: This method initializes an array with a predefined value efficiently in one step.
   - **Cons**: While `fill` is generally quick, creating filled arrays and then mapping over them can afford some overhead for large arrays.

6. **Array.from**
   - **Definition**: 
     - Version 1: `Array.from({ length: 1000 }).map((item, i) => {});`
     - Version 2: `Array.from({ length: 1000 }, (item, i) => i);`
   - **Pros**: `Array.from()` is a versatile method that can create an array from array-like or iterable objects. The second version allows for transforming directly during initialization.
   - **Cons**: The overhead associated with creating an object to pass length could slow down performance relative to some of the simpler methods.

### Performance Results:

The benchmark results provide the number of executions per second for each method under the same environment:

- **Fastest**: `Array(1000).fill(null)` with 386,268 executions/sec.
- **Followed By**: `[...Array(1000)]` at 375,066 executions/sec.
- Then `Array.push` at 325,620 executions/sec, and so on.
- The slowest was from methods involving `Array.from`, which falls behind the standard array creation methods.

### General Considerations:

- Performance can vary greatly based on the JavaScript engine and the implementation specifics of each method. It is essential to profile the methods in the intended environment.
- Readability and maintainability of code are also crucial. Some developers might prefer newer syntaxes like spread and destructuring for cleaner code, even if they come with a performance cost.
- If performance is critical, opting for the fastest methods identified in benchmarks would be advisable.
- Other alternatives could include using libraries such as **Lodash** or **Underscore.js**, which offer utility functions for array manipulation, though incorporating them might introduce additional overhead and dependencies.

This ensures that developers have a comprehensive understanding of different practices for creating arrays in JavaScript and can select the best approach based on their performance requirements and code style preferences.

Related benchmarks:

compare the ways to generate an array filled with empty objects for iteration (version: 1)

- Array.push - Array.apply: Array.apply(null, Array(100)) - Destructuring operator: [...Array(100)] - Array.prototype.fill Array(100).fill(undefined) - Array.from Array.from({ length: 100 })

Comparing performance of: Array.apply(null, Array(n)) vs [...Array(n)] vs Array(n).fill(null) vs Array.from({ length: n }) vs Array.from({ length:n }, (item, i) => i) vs Array.push vs Array with length + push

Created: 2 months ago by: Guest

Jump to the latest result

Array.apply(null, Array(n))

[...Array(n)]

Array(n).fill(null)

Array.from({ length: n })

Array.from({ length:n }, (item, i) => i)

Array.push

Array with length + push

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 months ago):