Benchmark: Array Spread vs slice

Tests:

Slice
const testArray = [{foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}]; const testArray2 = testArray.slice();
Spread
const testArray = [{foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}]; const testArray2 = [...testArray]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Slice
Spread

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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Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Definition and Preparation Code**

The provided JSON represents a benchmark definition, which is a set of rules for creating a specific test case. In this case, the benchmark definition is simple:

* The name of the benchmark is "Array Spread vs slice".
* There is no description.
* No script preparation code or HTML preparation code are required.

**Individual Test Cases**

There are two individual test cases:

1. **Slice**
The first test case uses the `slice()` method to create a shallow copy of an array. The benchmark definition shows how this method is used:
```javascript
const testArray = [{foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}];
const testArray2 = testArray.slice();
```
In modern JavaScript, `slice()` creates a new array object and returns a reference to it. It does not create a deep copy of the original array.

2. **Spread**
The second test case uses the spread operator (`...`) to create a shallow copy of an array. The benchmark definition shows how this method is used:
```javascript
const testArray = [{foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}];
const testArray2 = [...testArray];
```
In modern JavaScript, the spread operator creates a new array object and returns a reference to it. It does not create a deep copy of the original array.

**Pros and Cons**

Here are some pros and cons of each approach:

* **Slice()**
	+ Pros:
		- Widely supported across browsers.
		- Can be used in older JavaScript versions (before ES6).
	+ Cons:
		- Creates a shallow copy, not a deep copy.
		- May be slower than the spread operator for large arrays.
* **Spread Operator (`...`**
	+ Pros:
		- Creates a new array object and returns a reference to it.
		- Can create a deep copy if used with `Array.prototype.slice()` or other methods that support deep copying.
		- Faster than `slice()` for large arrays.
	+ Cons:
		- Introduced in ES6, so may not be supported in older browsers.

**Library: None**

There are no external libraries required for these test cases.

**Special JS Feature/ Syntax: None**

There are no special JavaScript features or syntax used in these test cases. The spread operator is a standard feature introduced in ES6.

**Other Alternatives**

If you need to create a deep copy of an array, you can use `Array.prototype.slice()` and then call the `concat()` method on the result:
```javascript
const testArray = [{foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}];
const testArray2 = testArray.slice().concat();
```
Alternatively, you can use a library like Lodash's `cloneDeep()` function to create a deep copy of the array:
```javascript
const _ = require('lodash');
const testArray = [{foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}, {foo: 'baz'}];
const testArray2 = _.cloneDeep(testArray);
```
Keep in mind that these alternatives may have performance implications and are not as efficient as using the spread operator or `slice()` directly.

Related benchmarks:

Array Spread vs slice (version: 0)

Comparing performance of: Slice vs Spread

Created: 4 years ago by: Guest

Jump to the latest result

Slice

Spread

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):