Benchmark: push vs set length and index

Tests:

push
const arr = [] const length = 100000 for(let i = 0; i < length; i++) { arr.push(i, 1) } console.log(arr[0], arr[100], arr[1000], arr[10001], arr[20000])
index
const arr = [] const length = 100000 arr.length = length*2+1 for(let i = 0; i < length; i++) { arr[i*2] = i; arr[i*2+1] = 1; } console.log(arr[0], arr[100], arr[1000], arr[10001], arr[20000])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
push
index

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36 Edg/135.0.0.0

Browser/OS: Chrome 135 on Windows

View result in a separate tab

Test name	Executions per second
push	649.6 Ops/sec
index	2651.1 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Description**
The benchmark is comparing two approaches to dynamically resize an array in JavaScript: `push` vs `set length and index`.

**Options Compared**

1. **Push**: The first approach uses the `push` method to add elements to the end of the array, incrementing its length.
2. **Set Length and Index**: The second approach manually sets the length of the array using the `length` property and then assigns values to specific indices.

**Pros and Cons**

1. **Push**:
	* Pros: Simple, efficient, and widely supported in modern browsers.
	* Cons: Can be slower for large arrays due to the overhead of incrementing the length property.
2. **Set Length and Index**:
	* Pros: Can be faster for large arrays since it avoids incrementing the length property, but requires manual memory management (assigning values directly).
	* Cons: More error-prone and less intuitive, as it relies on knowing the correct index-to-value mapping.

**Library/ Framework Considerations**
There are no specific libraries or frameworks being tested in this benchmark. However, some JavaScript engines might optimize certain array operations differently due to their implementation specifics.

**Special JS Features/Syntax**
The benchmark does not use any special JavaScript features or syntax beyond what's standard in modern JavaScript. There are no advanced topics like async/await, generators, or ES6 modules being tested.

**Other Alternatives**
For dynamic array resizing, other approaches exist, such as:

1. Using a library like Lodash's `tail` function to manipulate arrays without creating new ones.
2. Implementing a custom growth strategy using a queue or deque data structure.
3. Using WebAssembly (WASM) and a WASM runtime to execute code optimized for array performance.

**Benchmark Results**
The latest benchmark results show:

* The "index" test performed better than the "push" test, executing approximately 3.25 times more often per second on a Firefox 114 browser.
* However, without more context or data, it's difficult to conclude whether this result is statistically significant or if other factors influenced the outcome.

Keep in mind that benchmark results can be sensitive to system, network, and hardware conditions, so take these numbers with a grain of salt.

Related benchmarks:

push vs set length and index (version: 0)

Comparing performance of: push vs index

Created: 2 years ago by: Guest

Jump to the latest result

push

index

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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