var arr = [];
for (let i = 0; i < 1000; i++) {
arr[i] = i;
}
var len = arr.length
arr.forEach(item => item);
for (let i = 0; i < len; i++) {
return arr[i];
}
arr.map(item => item);
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
foreach | |
for | |
map |
Test name | Executions per second |
---|---|
foreach | 3002945.0 Ops/sec |
for | 8065733.0 Ops/sec |
map | 421831.2 Ops/sec |
Let's dive into explaining the provided benchmark.
What is tested on the provided JSON?
The provided JSON represents three microbenchmarks that test the performance of JavaScript loops: foreach
, for
, and map
. The benchmarks are designed to measure which loop construct is fastest for performing a simple array operation. Specifically, each benchmark creates an empty array, populates it with numbers from 0 to 999 using a loop, and then measures the time taken to execute the loop.
Options compared
The three options being compared are:
foreach
(.forEach()
method)for
(traditional loop syntax)map
(.map()
method)These options represent different approaches to iterating over an array in JavaScript.
Pros and cons of each approach:
.forEach()
method is a concise way to iterate over an array, but it's often slower than traditional loops because of the overhead of calling the callback function for each element. It also has performance implications when dealing with large arrays or complex operations..forEach()
method calls..map()
method is another concise way to iterate over an array, but it's often slower than traditional loops because of the overhead of creating a new array and calling the callback function for each element. It also has performance implications when dealing with large arrays or complex operations.Other considerations:
Library and special JS features:
None of the provided benchmarks rely on any external libraries. However, they do utilize some standard JavaScript features:
let
and const
: The benchmark uses let
and const
for variable declarations to ensure that the variables are not hoisted.=>
): Two of the benchmarks use arrow functions (.forEach()
and .map()
) which can be useful when writing concise code.Alternative approaches:
There are other loop constructs available in JavaScript, such as:
while
: A traditional loop construct that uses a conditional statement to control the iteration.for...in
: A loop construct that iterates over an object's property names.reduce()
: A method that reduces an array of values into a single output value.These alternative approaches may have their own performance implications and use cases, and are not directly comparable to the .forEach()
and traditional loops.