function test1(){
const x = 1+1;
return x;
}
function test1(){
return 1+1;
}
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
Var | |
No var |
Test name | Executions per second |
---|---|
Var | 523226656.0 Ops/sec |
No var | 515813632.0 Ops/sec |
Let's break down the JavaScript microbenchmark on MeasureThat.net and explain what's being tested, compared, and other considerations.
What is being tested?
The benchmark measures the performance difference between two approaches: using the var
keyword to declare variables versus not declaring them at all (i.e., using function scope).
Options compared:
Two options are being compared:
var
keyword to declare a variable inside the function.var
keyword, effectively using function scope instead.Pros and Cons of each approach:
var
keyword may not be supported.var
. However, it also means that variable declarations are implicit, which can make the code harder to understand and maintain.Other considerations:
In JavaScript, variables declared with var
have function scope, while variables declared without var
(or using let
or const
) have block scope. This means that in a single function, variables declared without var
are only accessible within the function's body, whereas those declared with var
are accessible throughout the entire function.
Library usage:
None of the benchmark cases use any JavaScript libraries.
Special JS features or syntax:
The benchmark uses some implicit variable scoping rules in modern browsers. Specifically, it relies on the fact that variables declared without var
, let
, or const
have block scope. This is a feature introduced in ECMAScript 2015 (ES6) and is supported by most modern JavaScript engines.
Benchmark preparation code:
The provided benchmark preparation code is empty, which means that MeasureThat.net likely generates this code automatically based on the benchmark definition.
Alternatives:
Other alternatives to measure variable declaration performance could include:
var
, let
, or const
on memory usage.These alternative benchmarks could provide more comprehensive insights into the performance implications of variable declaration choices in JavaScript.