Benchmark: Last item in array pop vs array position

Script Preparation code:

var arr = [];
for (let i = 0; i < 100; i++) {
    arr.push({
        i,
        route: {
            mode: 'bus'
        }
    });
}

Tests:

pop
arr.map((departure) => departure.route.mode).pop() || 'bus';
position 0
arr[0].route.mode || bus

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
pop
position 0

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/106.0.0.0 Safari/537.36 Edg/106.0.1370.52

Browser/OS: Chrome 106 on Windows

View result in a separate tab

Test name	Executions per second
pop	847752.8 Ops/sec
position 0	3522333.8 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark.

**Benchmark Definition**

The benchmark is designed to measure the performance difference between two approaches:

1. `arr.map((departure) => departure.route.mode).pop() || 'bus';`
2. `arr[0].route.mode || 'bus'`

These two expressions aim to access and return the value of `mode` from an object in an array.

**Options Compared**

The benchmark compares the performance of these two approaches:

* Approach 1 uses `map`, which creates a new array with transformed values, and then `pop()` to remove the last element. If there are no elements, it returns `'bus'`.
* Approach 2 directly accesses the first element (`arr[0]`) and its `route.mode` property.

**Pros and Cons of Each Approach**

* **Approach 1 (Using map)**:
	+ Pros: This approach is more flexible, as it can be easily applied to any array. It also avoids indexing into the array directly.
	+ Cons: Creating a new array with transformed values incurs additional memory allocation and copy operations, which can lead to performance overhead.
* **Approach 2 (Directly accessing `arr[0]`)**:
	+ Pros: This approach is faster, as it only accesses a single element in the array. It also avoids unnecessary array creation.
	+ Cons: This approach is less flexible and may not work if the first element changes.

**Library Usage**

There is no explicit library mentioned in this benchmark. However, `map` is a built-in JavaScript method that works on arrays. The `|| 'bus'` syntax suggests using the nullish coalescing operator (`??`), which was introduced in ECMAScript 2020 (JavaScript 2021). This operator returns the first operand if it's not null or undefined, and the second operand otherwise.

**Special JS Feature/Syntax**

The benchmark uses the nullish coalescing operator (`|| 'bus'`) to provide a default value if `arr[0].route.mode` is null or undefined. This syntax is specific to ECMAScript 2020 (JavaScript 2021).

**Other Alternatives**

If you were to rewrite this benchmark for an older JavaScript version, you might use:

* For Approach 1: `map((departure) => departure.route.mode).pop()`
* For Approach 2: `arr[0].route.mode`

However, the nullish coalescing operator (`|| 'bus'`) is not available in earlier versions of JavaScript.

Keep in mind that this benchmark is designed to measure performance differences between these two approaches. The results might vary depending on the specific use case and implementation details.

Related benchmarks:

Last item in array pop vs array position (version: 0)

Comparing performance of: pop vs position 0

Created: one year ago by: Guest

Jump to the latest result

pop

position 0

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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