Benchmark: spread vs push vs ifSpread vs ifPush

Script Preparation code:

var arr1 = [1,32,4,34,5,6,7,34,5,6];
var arr2 = [5,232,545,56,223,5,1,6,30];

Tests:

spread
var resultSpread = [...arr1, ...arr2];
push
for (let index = 0; index < arr2.length; index++) { const element = arr2[index]; arr1.push(element); }
ifPush
for (let index = 0; index < arr2.length; index++) { const element = arr2[index]; if (arr1.findIndex((item) => item === element) < 0) { arr1.push(element); } }
ifSpread
for (let index = 0; index < arr2.length; index++) { const element = arr2[index]; if (arr1.findIndex((item) => item === element) < 0) { arr1 = [...arr1, element]; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
spread
push
ifPush
ifSpread

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

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

The benchmark is comparing four different approaches to concatenate (join) two arrays, `arr1` and `arr2`, into a new array:

1. Using the spread operator (`...`)
2. Using the `push()` method
3. Using the `findIndex()` method with an if statement to check for existence before pushing
4. Using the spread operator (`...`) inside the `arr1` array assignment

Let's analyze each approach and its pros and cons:

**1. Spread Operator (`...`)**

* Pros: concise, readable, and efficient. It creates a new array by copying elements from `arr2` and appending them to `arr1`.
* Cons: may incur additional overhead due to the creation of a new array.

**2. Push() Method**

* Pros: straightforward, easy to understand, and efficient for large arrays.
* Cons: requires iterating over `arr2` and pushing each element into `arr1`, which can be slower than using spread or findIndex.

**3. findIndex() Method with if Statement**

* Pros: cleverly avoids creating a new array, only iterating over `arr2` once, and efficiently checks for existence in `arr1`.
* Cons: may require careful handling of edge cases (e.g., when `arr1` is empty), can be less readable than other approaches.

**4. Spread Operator (`...`) Inside Array Assignment**

* Pros: similar to the spread operator approach, but creates a new array by copying elements from `arr2` and assigning it to `arr1`.
* Cons: slightly slower due to the additional assignment operation.

Other considerations:

* The benchmark is testing these approaches on a large array of numbers (`[1, 32, 4, ...]`) which might affect performance.
* The use of `findIndex()` with an if statement allows for efficient existence checks in `arr1` without creating a new array.
* The spread operator and spread operator inside array assignment are similar approaches but differ slightly in implementation.

Now, about the libraries used:

None of the benchmark's test cases explicitly use any external libraries. However, it is worth noting that modern JavaScript environments (like those tested by MeasureThat.net) come with built-in functions like `findIndex()` which are equivalent to using external libraries like Lodash.

Special JS features or syntax:

There are no special features or syntax used in this benchmark beyond what's considered standard for modern JavaScript. The use of spread operator and `findIndex()` is a common, idiomatic way to accomplish these operations in recent JavaScript versions (ES6+).

For those interested in alternatives:

Other methods for concatenating arrays include:

* Using the `concat()` method: `arr1.concat(arr2)`
* Using `Array.prototype.reduce()`: `[...arr1, ...arr2]`
* Using `Array.prototype.forEach()`: `arr1.forEach((item) => arr2.push(item));`

Each of these alternatives has its own pros and cons, but they are generally less efficient or more verbose than the approaches tested in this benchmark.

Related benchmarks:

spread vs push vs ifSpread vs ifPush (version: 0)

Comparing performance of: spread vs push vs ifPush vs ifSpread

Created: 5 years ago by: Guest

Jump to the latest result

spread

push

ifPush

ifSpread

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):