var arr = Array(100000).fill(1);
arr[arr.length - 1];
arr[arr.length - 1];
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
arr.slice(-1)[0] | |
arr.at(-1) |
Test name | Executions per second |
---|---|
arr.slice(-1)[0] | 14038803.0 Ops/sec |
arr.at(-1) | 14094083.0 Ops/sec |
I'd be happy to explain the JavaScript microbenchmark.
What is being tested?
The provided benchmark is comparing two approaches to accessing the last element of an array in JavaScript:
arr.at(-1)
arr[arr.length - 1]
arr.slice(-1)[0]
These three options are being compared to determine which one is the fastest.
Options comparison
Here's a brief overview of each option:
arr.at(-1)
: This method was introduced in ECMAScript 2019 (ES11) as part of the Array.prototype.at() method, which provides an alternative way to access array elements by their index or property key.arr[arr.length - 1]
: This is a common and straightforward approach to accessing the last element of an array in JavaScript. It involves concatenating the string representation of arr.length
with -1
, creating a new expression that calculates the index, and then using it to access the element.arr.slice(-1)[0]
: This method uses the slice()
method to create a shallow copy of the array's last element, and then accesses the first (and only) element of the resulting array.Pros and Cons of each approach
Here are some pros and cons for each option:
arr.at(-1)
arr.length
with -1
arr[arr.length - 1]
arr[0]
)arr.slice(-1)[0]
arr.length
with -1
slice()
) which can be slowerLibrary usage
There is no library used in this benchmark. All the code is native JavaScript.
Special JS feature or syntax
No special features or syntax are mentioned in the provided benchmark.
Other alternatives
If you need to access array elements, other alternatives could include:
for...in
loop: Accessing elements using a for...in
loop can be slower than array methods.Math.floor()
: Using Math.floor(arr.length / 2)
or similar calculations to estimate the middle index can be slower and less accurate than using array methods.Keep in mind that the choice of approach depends on the specific use case, performance requirements, and compatibility constraints.