Benchmark: Array .push() vs .unshift()

Script Preparation code:

var arr = []

Tests:

.push()
arr.push(42)
.unshift()
arr.unshift(42)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:135.0) Gecko/20100101 Firefox/135.0

Browser/OS: Firefox 135 on Linux

View result in a separate tab

Test name	Executions per second
.push()	16548820.0 Ops/sec
.unshift()	8693.2 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks!

The provided JSON represents a benchmark test on MeasureThat.net, which compares the performance of two approaches: using the `push()` method versus the `unshift()` method when adding an element to an empty array.

**What is being tested?**

The test checks how fast each approach can add an element (in this case, the number 42) to an empty array. The `push()` method adds an element to the end of the array, while the `unshift()` method adds an element to the beginning of the array.

**Options compared:**

There are two options being compared:

1. **`arr.push(42)`**: This is the traditional way to add an element to the end of an array using the `push()` method.
2. **`arr.unshift(42)`**: This approach adds an element to the beginning of the array using the `unshift()` method.

**Pros and cons:**

* **`arr.push(42)`**:
	+ Pros:
		- More common and widely used
		- Easier to implement
	+ Cons:
		- Can be slower due to the need to shift elements down when adding an element to the end
* **`arr.unshift(42)`**:
	+ Pros:
		- Faster than `push()` because it can avoid shifting elements down
	+ Cons:
		- Less common and less widely used, which may make it harder for other developers to understand

In general, `push()` is a safer choice if you're working with large arrays or need to add elements frequently. However, if you're only adding one element at a time and don't care about performance, `unshift()` might be faster.

**Library usage:**

There is no library explicitly mentioned in the JSON, but we can assume that the `Array` prototype is being used as intended by both `push()` and `unshift()` methods. These methods are built-in to JavaScript and do not require any external libraries.

**Special JS features or syntax:**

This benchmark does not use any special JavaScript features or syntax. It only uses standard JavaScript language elements, such as arrays and the `push()` and `unshift()` methods.

**Alternative approaches:**

If you want to explore alternative approaches for adding elements to an array, here are a few options:

1. **Using `concat()`**: Instead of using `push()` or `unshift()`, you can use the `concat()` method to create a new array with the added element.
2. **Using `slice()` and `Array.prototype.push()`:** You can use `slice()` to extract a subset of an array, push a new element onto it, and then return the resulting array.

For example:
```javascript
var arr = [];
arr = arr.concat(42);
```
or
```javascript
var arr = [];
arr = arr.slice().concat(42);
```
Keep in mind that these approaches may have different performance characteristics compared to using `push()` or `unshift()`.

Related benchmarks:

Array .push() vs .unshift() (version: 0)

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

Created: 9 years ago by: Guest

Jump to the latest result

.push()

.unshift()

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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