var arr = [];
for (let i = 0; i < 50; i++){
arr.unshift(i);
}
for (let i = 0; i < 50; i++){
arr.push(i);
}
arr.reverse();
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
unshift | |
push + reverse |
Test name | Executions per second |
---|---|
unshift | 830.3 Ops/sec |
push + reverse | 2224.7 Ops/sec |
Let's break down the provided benchmark and explain what's being tested.
Benchmark Overview
The benchmark compares two approaches to add elements to an array: arr.unshift(i)
and arr.push(i) + arr.reverse()
. The test case creates an empty array, fills it with 50 elements using one of these methods, and then measures the execution time.
Options Compared
There are two options being compared:
arr.push(i)
, and then reverses the entire array using arr.reverse()
.Pros and Cons
push
because it involves updating an internal array structure, which can lead to cache misses.unshift
because reversing the entire array at once can reduce cache locality issues. However, this approach is less efficient for small arrays or frequent insertions.Library
The benchmark does not use any external libraries beyond what's built into JavaScript (e.g., Array.prototype.unshift
, Array.prototype.push
, Array.prototype.reverse
).
Special JS Feature or Syntax
There is no special JS feature or syntax being tested in this benchmark. The focus is on the performance comparison between two common array manipulation methods.
Other Considerations
unshift
method may perform better if the array grows quickly because it only requires updating indices, while push + reverse
involves reversing the entire array.Other Alternatives
If you're interested in exploring other approaches or variations, consider these alternatives:
unshift
and push
, use splice
to remove and add elements from the array.concat
versus creating a new array with push
.for (var i = 0; i < 50; ++i) { arr[i] = i; }
) versus using built-in array methods like forEach
, map
, or reduce
.arr = new Array(50);
) compares to dynamically allocating memory using new Int32Array()
or other native array types.Keep in mind that these alternative benchmarks will likely have different test cases and focus on specific aspects of JavaScript performance.