Benchmark: Array.prototype.slice vs spread operator vs concat

Tests:

Array.prototype.slice
var params = [ "hello", true, 7 ]; var other = params.slice();
spread operator
var params = [ "hello", true, 7 ] var other = [ ...params ]
concat
var params = [ "hello", true, 7 ] var other = [].concat(params)

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Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.prototype.slice
spread operator
concat

Fastest: N/A

Slowest: N/A

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

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Measuring the performance of JavaScript array operations is crucial for optimizing code and ensuring efficient execution. Let's break down the provided benchmark.

**Benchmark Definition:**
The benchmark compares three methods to create a copy of an array:

1.  **`Array.prototype.slice()`**: This method returns a shallow copy of a portion of an array, starting from the beginning.
2.  **Spread Operator (`...`)**: Introduced in ES6, this operator creates a new array by spreading elements from an existing array or other iterable.
3.  **`concat()`**: This method returns a new array that is the result of concatenating two arrays.

**Options Compared:**
The benchmark compares these three options:

*   `Array.prototype.slice()`
*   Spread Operator (`...`)
*   `concat()`

**Pros and Cons of Each Approach:**

1.  **`Array.prototype.slice()`**: This method creates a new array with the specified start index, but it doesn't create a deep copy.
    *   Pros:
        *   Fast execution
        *   Wide browser support
    *   Cons:
        *   May not be suitable for deep copying or large arrays

2.  **Spread Operator (`...`)**: This operator creates a new array by spreading elements from an existing array or other iterable.
    *   Pros:
        *   Efficient and fast execution
        *   Easy to use and understand
        *   Suitable for both shallow and deep copies
    *   Cons:
        *   May have slightly worse performance due to the overhead of creating a new array

3.  **`concat()`**: This method creates a new array that is the result of concatenating two arrays.
    *   Pros:
        *   Simple and intuitive usage
    *   Cons:
        *   Inefficient execution compared to slice() or spread operator
        *   May have worse performance due to creating multiple intermediate arrays

**Library/Functionality:**
None of these options rely on external libraries. They are all part of the JavaScript standard library.

**Special JS Feature/Syntax:**
The benchmark uses the spread operator (`...`), which is a feature introduced in ES6 (ECMAScript 2015). This syntax allows for creating new arrays by spreading elements from existing iterables.

**Other Alternatives:**

1.  **`Array.prototype.push()` with an initial length**: You can use `push()` method to create an array and then use the spread operator to copy its contents.
    ```javascript
let arr = [ 'hello', true, 7 ];
arr.push(...arr.slice(1)); // copies all elements except the first one
```
2.  **`Array.from()`**: Introduced in ES6, this method creates a new array from an iterable or array-like object.
    ```javascript
let arr = [ 'hello', true, 7 ];
let newArr = Array.from(arr); // creates a shallow copy of the original array
```

In summary, the benchmark compares three common ways to create a copy of an array in JavaScript: `Array.prototype.slice()`, Spread Operator (`...`), and `concat()`. Each approach has its pros and cons, and understanding these differences can help developers choose the most efficient solution for their use cases.

Related benchmarks:

Array.prototype.slice vs spread operator vs concat (version: 0)

Compare the new ES6 spread operator with the traditional slice() method

Comparing performance of: Array.prototype.slice vs spread operator vs concat

Created: 4 years ago by: Guest

Jump to the latest result

Array.prototype.slice

spread operator

concat

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):