const ITERATIONS = 500000;
var index = ITERATIONS/2;
var n = Math.random();
var list = [];
for (let i = 0; i < length; i += 1) {
list.push(Math.random());
}
const clone = [list];
const clone = list.slice();
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
Array clone with spread operator | |
Array clone with slice |
Test name | Executions per second |
---|---|
Array clone with spread operator | 5997487.5 Ops/sec |
Array clone with slice | 15556043.0 Ops/sec |
Let's break down the benchmark and analyze what's being tested.
Benchmark Overview
The benchmark measures the performance of two ways to create a shallow copy of an array in JavaScript: using the spread operator (...
) and using the slice()
method. The test is designed to identify which approach is faster, more efficient, and scalable.
Test Case 1: Array clone with spread operator
In this test case, the benchmark creates an array list
with a random length (between 0 and the total number of iterations) and then uses the spread operator (...
) to create a shallow copy of the array. The code is as follows:
const clone = [...list];
Test Case 2: Array clone with slice
In this test case, the benchmark creates an array list
with a random length (between 0 and the total number of iterations) and then uses the slice()
method to create a shallow copy of the array. The code is as follows:
const clone = list.slice();
Options Compared
The two test cases compare the performance of:
...
): creates a new array by spreading the original array's elements.slice()
): returns a shallow copy of a portion of an array, starting at the specified index.Pros and Cons of Each Approach
...
)[...array, [innerArray]]
).slice()
)Library Used
In this benchmark, no libraries are explicitly mentioned. However, it is worth noting that the slice()
method is part of the JavaScript standard library and has been available since ECMAScript 5 (2011).
Special JS Feature or Syntax
There is no specific JavaScript feature or syntax being tested in this benchmark, as both test cases only use standard JavaScript constructs.
Other Considerations
When working with arrays, it's essential to consider factors such as:
The spread operator and slice method can have different effects on these factors, depending on the specific use case and performance requirements.
Alternatives
If you need to create a shallow copy of an array in JavaScript, other alternatives include:
Array.prototype.slice.call(array)
: creates a new array from the elements of another array.Array.prototype.reduce()
: can be used to create a new array by applying a reducer function to each element of the original array.cloneDeep()
or Immutable.js, which provide more advanced data structure manipulation capabilities.In conclusion, this benchmark measures the performance of two ways to create a shallow copy of an array in JavaScript: using the spread operator and the slice method. Understanding the pros and cons of each approach can help you choose the most efficient solution for your specific use case.