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Array .concat() vs .unshift()
(version: 0)
Comparing performance of:
arr.unshift(42) vs [42].concat(arr)
Created:
5 years ago
by:
Guest
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Script Preparation code:
var arr = []
Tests:
arr.unshift(42)
arr.unshift(42)
[42].concat(arr)
[42].concat(arr)
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
arr.unshift(42)
[42].concat(arr)
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's dive into the explanation of the provided benchmark. **What is being tested?** The benchmark measures the performance difference between two approaches to add an element to the end of an array: `arr.unshift(42)` and `[42].concat(arr)`. The goal is to determine which approach is faster. **Options compared** There are only two options being compared: 1. `arr.unshift(42)`: This method adds a new element to the beginning of the array. It shifts all existing elements down by one position, making room for the new element. 2. `[42].concat(arr)`: This method creates a new array with the original array as its first element and the new number `42` as its second element. **Pros and Cons** **1. arr.unshift(42)** Pros: * Efficient use of memory, as it only adds one new element to the existing array. * Fast execution time, as it's a simple operation that only requires updating the array's length. Cons: * Can be slower than concatenation for very large arrays, since shifting elements can lead to slower cache performance. * May not be suitable for arrays with many null or undefined values, as it can lead to unnecessary shifts. **2. [42].concat(arr)** Pros: * Suitable for large arrays, as it creates a new array and doesn't modify the original one. * Fast execution time, since it's just an array concatenation operation. Cons: * Less memory-efficient than `unshift`, as it creates a new array with two elements: the original array and the new number. * Can be slower for small arrays due to the overhead of creating a new array. **Library and its purpose** In this benchmark, the JavaScript Array class is used. The Array class provides methods like `push()`, `unshift()`, and `concat()` that allow developers to manipulate array elements. **Special JS feature or syntax** There is no special JavaScript feature or syntax being tested in this benchmark. However, it's worth noting that this benchmark might not be representative of real-world scenarios, as it only tests two specific methods on a small array. In practice, you may encounter different performance characteristics when working with larger arrays or more complex data structures. **Other alternatives** If you wanted to test other approaches for adding elements to an array, some additional options could include: * Using `Array.prototype.push()` instead of `unshift()` * Using `Array.prototype.splice()` to insert a new element at a specific position * Using `Array.prototype.set()` if you're working with older browsers that support this method However, these alternatives are not being tested in this benchmark.
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Array concat vs. spread operator
Concat() vs. Unshift()
Unshift vs concat
Array add vs .unshift() 2
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