Benchmark: Array .push() vs .unshift(), 100K elements

Script Preparation code:

var arr = []

Tests:

.unshift()
for (var i = 0; i < 100000; i++) { arr.unshift(42) }
.push()
for (var i = 0; i < 100000; i++) { arr.push(42) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.unshift()
.push()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36 Edg/85.0.564.41

Browser/OS: Chrome 85 on Windows

View result in a separate tab

Test name	Executions per second
.unshift()	0.1 Ops/sec
.push()	85.3 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Definition**

The provided JSON represents a benchmark test case that measures the performance difference between two JavaScript methods: `arr.push()` and `arr.unshift()`. The benchmark is designed to push 100,000 elements onto an array (`var arr = []`) using both methods.

**Options Compared**

Two options are compared in this benchmark:

1. `.push()`: This method adds a new element to the end of an array.
2. `.unshift()`: This method adds a new element to the beginning of an array.

**Pros and Cons of Each Approach**

* `arr.push()`:
	+ Pros: Generally faster and more efficient, as it doesn't need to shift existing elements to make room for the new one.
	+ Cons: May require more memory allocation if the array grows rapidly.
* `.unshift()`:
	+ Pros: Can be useful when you need to add an element at the beginning of an array, especially if you're working with a large dataset.
	+ Cons: Generally slower and less efficient than `push()`, as it requires shifting existing elements.

**Library Used**

None is explicitly mentioned in the provided JSON. However, it's likely that the benchmark uses built-in JavaScript methods or libraries like V8 (Chrome's JavaScript engine) for execution.

**Special JS Feature/Syntax**

There are no specific features or syntax mentioned in the provided code. However, it's worth noting that modern JavaScript engines often employ various optimizations and techniques to improve performance, such as:

* Just-In-Time (JIT) compilation
* Ahead-of-Time (AOT) compilation
* Optimized data structures

**Other Considerations**

* Array allocation and deallocation can have a significant impact on performance.
* The benchmark only measures the execution time of `push()` and `unshift()`. To get a more comprehensive understanding of an array's performance, you might want to consider measuring other aspects, such as memory usage or cache efficiency.

**Alternatives**

If you're interested in exploring alternative benchmarks or optimizing JavaScript performance, here are some alternatives:

* Benchmarking libraries like Benchmark.js or Benchmark-Helper
* Microbenchmarking frameworks like Jest-Microtasks or Benchmark
* Performance testing tools like Chrome DevTools' Perf panel or Node.js Inspector

Keep in mind that the choice of benchmarking library or tool often depends on your specific use case, JavaScript version, and desired level of complexity.

Related benchmarks:

Array .push() vs .unshift(), 100K elements (version: 0)

Comparing performance of: .unshift() vs .push()

Created: 4 years ago by: Guest

Jump to the latest result

.unshift()

.push()

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):