Benchmark: var-let-const2 - MeasureThat.net

Tests:

const
const g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o() window.g = g;
let
let g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o() window.g = g;
var
var g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o() window.g = g;

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Other 7 runs

const

12.2M/s

let

8.9M/s

var

8.8M/s

Fastest: const (1.4x faster)

View exact numbers

✓ const: 12,157,679 ops/sec
• let: 8,861,972 ops/sec
• var: 8,845,912 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
const
let
var

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36 OPR/113.0.0.0

Browser/OS: Opera 113 on Windows

View result in a separate tab

const

12.3M/s

let

6.9M/s

var

5.9M/s

View exact numbers

Test name	Executions per second
✓ const	12,283,043 Ops/sec
let	6,907,151 Ops/sec
var	5,873,481 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its test cases to understand what is being tested.

**Benchmark Definition:**
The provided JSON represents a JavaScript microbenchmarking framework, where users can create and run benchmarks for different programming constructs (in this case, `var`, `let`, and `const`). The benchmark definition includes a script preparation code, which is empty in this example. This suggests that the focus is on comparing the performance of these three variables across different browsers.

**Test Cases:**
The individual test cases are as follows:

1. `const g = { e: [] }ng.o = function(x) { g.e.push(...[1,2,3]) }ng.o()window.g = g;`
	* This test case creates a constant object `g` with an empty array `e`, then defines a function `o` that pushes elements into the array. The function is called twice, and finally, the `g` object is assigned to the global scope.
2. `let g = { e: [] }ng.o = function(x) { g.e.push(...[1,2,3]) }ng.o()window.g = g;`
	* Similar to the previous test case, but uses a `let` variable instead of `const`.
3. `var g = { e: [] }ng.o = function(x) { g.e.push(...[1,2,3]) }ng.o()window.g = g;`
	* This test case is similar to the first one, but uses a `var` variable.

**Comparison of Options:**

* **Var**: In this benchmark, the `var` option is tested in the context of modern JavaScript engines. The use of `var` can lead to hoisting issues and potential performance regressions.
	+ Pros:
		- Familiarity for developers who have used older versions of JavaScript.
		- Some argue that `var` is a more straightforward way to declare variables.
	+ Cons:
		- Hoisting issues can lead to unexpected behavior.
		- In some cases, `var` can be slower than `let` or `const`.
* **Let**: This option tests the use of `let` in modern JavaScript engines. `let` introduces block scope and is generally considered a better choice for variable declarations.
	+ Pros:
		- Introduces block scope, reducing potential hoisting issues.
		- More explicit and readable code.
	+ Cons:
		- Some older browsers may not support it (although most modern ones do).
* **Const**: This option tests the use of `const` in modern JavaScript engines. `const` introduces immutability and is generally considered a best practice for variable declarations.
	+ Pros:
		- Introduces immutability, reducing potential side effects.
		- More explicit and readable code.
	+ Cons:
		- Some older browsers may not support it (although most modern ones do).

**Library Usage:**
There is no explicitly mentioned library in the provided benchmark definition. However, some libraries might be used indirectly through the use of modern JavaScript features.

**Special JS Features/Syntax:**
The test cases rely on modern JavaScript features such as:

* **Arrow Functions**: The `ng.o` function is defined using an arrow function syntax (`=>`).
* **Template Literals**: The `push(...[1,2,3])` expression uses template literals to create an array.
* **Spread Operator**: The `push(...[1,2,3])` expression also uses the spread operator (`...`) to expand the array.

**Other Alternatives:**
Some alternatives for this benchmark could include:

* Comparing the performance of these variables in older JavaScript engines (e.g., ECMAScript 5.1).
* Testing the memory usage or garbage collection behavior of each option.
* Adding more complex test cases that incorporate additional modern JavaScript features, such as async/await or classes.

Keep in mind that this is just an explanation based on the provided information, and there might be other considerations or alternatives not mentioned here.

var-let-const2 (version: 0)

Comparing performance of: `const vs let vs var`

Created: one year ago by: Guest

Go to the latest result

const

let

var

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Other 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

var-let-const2 (version: 0)

Comparing performance of: const vs let vs var

Created: one year ago by: Guest

Go to the latest result

const

let

var

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Other 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Related benchmarks

Comparing performance of: `const vs let vs var`