Benchmark: concat vs push vs spread performance

Tests:

Concat
var a = [ "hello", true, 7 ]; var b = [ 1, 2 ]; var c = a.concat(b);
Spread operator
var a = [ "hello", true, 7 ]; var b = [ 1, 2 ]; var c = [ ...a, ...b ]
Push
var a = [ "hello", true, 7 ]; var b = [ 1, 2 ]; var c = a.push(...b);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Concat
Spread operator
Push

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Concat	9372518.0 Ops/sec
Spread operator	29255606.0 Ops/sec
Push	53624148.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared, and their pros and cons.

**Benchmark Overview**

The test compares the performance of three approaches:

1. `concat()`
2. Spread operator (`...`)
3. `push()` with spread syntax (`...`)

All three methods are used to concatenate two arrays: `a` containing strings, booleans, and a number, and `b` containing numbers.

**Library Used**

There is no specific library used in this benchmark, but it's worth noting that some browsers might use polyfills or implementations of these methods if they're not available by default.

**Special JavaScript Feature/Syntax**

The test uses the spread operator (`...`) introduced in ES6 (ECMAScript 2015). This feature allows creating a new array by "spreading" elements from an existing array. It's also used with `push()` to spread elements into the original array.

Now, let's dive into each individual test case:

**Test Case 1: Concat**

* Benchmark Definition:
```javascript
var a = [ "hello", true, 7 ];
var b = [ 1, 2 ];
var c = a.concat(b);
```
This is the traditional way of concatenating arrays in JavaScript. The `concat()` method returns a new array and does not modify the original.

Pros:

* Widely supported across browsers
* Simple to implement

Cons:

* Creates a new array, which can be memory-intensive for large datasets

**Test Case 2: Spread Operator**

* Benchmark Definition:
```javascript
var a = [ "hello", true, 7 ];
var b = [ 1, 2 ];
var c = [...a, ...b];
```
The spread operator (`...`) creates a new array by spreading elements from the original arrays. This method is more concise and efficient than `concat()`.

Pros:

* More concise than `concat()`
* More efficient than `concat()`

Cons:

* Not supported in older browsers (pre-ES6)
* May have issues with non-array values being spread

**Test Case 3: Push**

* Benchmark Definition:
```javascript
var a = [ "hello", true, 7 ];
var b = [ 1, 2 ];
a.push(...b);
```
The `push()` method with spread syntax (`...`) modifies the original array by adding new elements at the end. This approach is more efficient than `concat()` but requires care when dealing with non-array values.

Pros:

* More efficient than `concat()`
* Modifies the original array

Cons:

* May have issues with non-array values being pushed
* Not as widely supported as `concat()`

**Other Alternatives**

If you need to concatenate arrays, other alternatives include using `Array.prototype.reduce()` or a custom implementation. However, these methods are less efficient and more complex than the three tested approaches.

In summary:

* For simple cases, `concat()` is a safe choice.
* For performance-critical code, consider using the spread operator (`...`) for its efficiency.
* When modifying the original array, use `push()` with spread syntax (`...`), but be mindful of non-array values being pushed.

Related benchmarks:

concat vs push vs spread performance (version: 0)

Compare the new ES6 spread operator with the traditional concat() method and push

Comparing performance of: Concat vs Spread operator vs Push

Created: 4 years ago by: Guest

Jump to the latest result

Concat

Spread operator

Push

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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