var g = { e: [] }g.o = function(x) { g.e.push([1,2,3]) }g.o()let g = { e: [] }g.o = function(x) { g.e.push([1,2,3]) }g.o()const g = { e: [] }g.o = function(x) { g.e.push([1,2,3]) }g.o()g = { e: [] }g.o = function(x) { g.e.push([1,2,3]) }g.o()--enable-precise-memory-info flag.
| Test case name | Result |
|---|---|
| var | |
| let | |
| const | |
| sloppy |
| Test name | Executions per second |
|---|---|
| var | 16082074.0 Ops/sec |
| let | 16132550.0 Ops/sec |
| const | 15292942.0 Ops/sec |
| sloppy | 13984633.0 Ops/sec |
I'll explain the benchmark being tested on MeasureThat.net.
What is being tested?
The provided benchmark tests the performance difference between four JavaScript variable scoping mechanisms: var, let, const, and "sloppy" (which is a non-standard, older syntax). The benchmark measures how many executions per second each variable scope allows for in a specific JavaScript function.
Options being compared:
var: The traditional variable scoping mechanism in JavaScript, where variables are scoped to the entire function.let: A newer variable scoping mechanism introduced in ES6 (ECMAScript 2015), which allows block-level scoping and re-declaration.const: Similar to let, but variables with const cannot be reassigned.: An older syntax, which is no longer supported in modern JavaScript versions. It was used before the introduction of var, let, and const`.Pros and Cons:
var: Pros: simple to use, widely supported. Cons: can lead to variable hoisting issues, pollutes global scope.let: Pros: block-level scoping, allows re-declaration with the same name in a different scope, improves code readability. Cons: not supported in older browsers or environments.const: Similar pros and cons as let, but adds an additional layer of safety against accidental re-assignment.Library usage
In the benchmark code, there is no explicit library mentioned. However, JavaScript's built-in Array.prototype.push method is used.
Special JS feature or syntax
There are no special features or syntaxes being tested in this benchmark. The only thing being varied is the variable scoping mechanism.
Other alternatives
For testing variable scoping mechanisms, you could consider other approaches:
Keep in mind that MeasureThat.net's approach is more focused on measuring the performance impact of different scoping mechanisms, making it a great resource for understanding how these differences affect execution speed.
