Benchmark: Test Unshift vs push + reverse

Script Preparation code:

var a = [];

Tests:

Push
for (let i=0; i<1000; i++){ a.push(i); } a.reverse()
Unshift
for (let i=0; i<1000; i++){ a.unshift(i); }

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:

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

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I'll break down the benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark is designed to compare the performance of two approaches: using `push` followed by `reverse`, and using `unshift`. The test case creates an empty array `a` and then adds 1000 elements to it using either `push` or `unshift`. After that, it reverses the array using the same method.

**Options Compared**

There are two options being compared:

1. **Using `push` followed by `reverse`**: This approach is also known as "in-place reversal" or " mutating the original array". The `push` method adds an element to the end of the array, and then the `reverse` method reverses the entire array in place.
2. **Using `unshift`**: This approach is also known as "adding elements to the beginning of the array". The `unshift` method adds one or more elements to the beginning of the array.

**Pros and Cons**

* Using `push` followed by `reverse`:
	+ Pros: generally faster, since reversing the entire array in place can be more efficient than creating a new reversed array.
	+ Cons: modifies the original array, which might not be desirable if the array is used elsewhere.
* Using `unshift`:
	+ Pros: doesn't modify the original array, which can be beneficial for preserving data integrity.
	+ Cons: might be slower due to the overhead of adding elements to the beginning of the array.

**Library and Special Features**

There are no libraries being used in this benchmark. However, it's worth noting that some JavaScript engines have built-in optimization techniques or caching that may affect the performance of these operations.

**Special JS Feature (if applicable)**

None of the options shown here use any special JavaScript features. They rely on standard JavaScript APIs and methods.

**Other Considerations**

* The benchmark assumes that the arrays are being used in a context where they need to be reversed, which might not always be the case.
* The benchmark doesn't consider other factors that could affect performance, such as array size, data distribution, or caching behavior.

**Alternatives**

There are alternative approaches to reversing an array in JavaScript:

1. Using `Array.prototype.slice()` followed by `Array.prototype.reverse()`: This approach creates a new reversed array instead of modifying the original one.
2. Using `Array.prototype.concat()` and then `Array.prototype.reverse()`: This approach also creates a new reversed array, but with more overhead due to the concatenation step.

Keep in mind that these alternatives may have different performance characteristics depending on the specific use case and JavaScript engine being used.

Related benchmarks:

Test Unshift vs push + reverse (version: 0)

Comparing performance of: Push vs Unshift

Created: 4 years ago by: Guest

Jump to the latest result

Push

Unshift

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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