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const vs let vs var (fixed) 234
(version: 0)
Benchmark.js
Comparing performance of:
var vs let vs const
Created:
2 years ago
by:
Guest
Go to the latest result
Tests:
var
var g = []; var f = function(x) { g.push(1,2,3) }; f()
let
let g = []; let f = function(x) { g.push(1,2,3) }; f()
const
const g = []; const f = function(x) { g.push(1,2,3) }; f()
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (3)
Previous results
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Test case name
Result
var
let
const
Fastest:
N/A
Slowest:
N/A
Latest run results:
Run details:
(Test run date:
4 months ago
)
User agent:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:149.0) Gecko/20100101 Firefox/149.0
Browser/OS:
Firefox 149 on Mac OS X 10.15
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Embed Benchmark Result
<iframe src="https://measurethat.net/Embed?id=628391" width="100%" height="500px"></iframe>
var
28.1M/s
let
23.2M/s
const
23.2M/s
View exact numbers
Test name
Executions per second
✓
var
28,076,868 Ops/sec
let
23,179,148 Ops/sec
const
23,154,714 Ops/sec
Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
I'd be happy to help you understand the provided benchmark. **Benchmark Overview** The benchmark is designed to compare the performance of three JavaScript variable declarations: `const`, `let`, and `var`. The test cases are identical, except for the declaration type. Each test case consists of a function that pushes an array of numbers onto a global array using the declared variable. **Options Compared** The options being compared are: 1. **`const`**: A declaration that ensures the variable cannot be reassigned. 2. **`let`**: A declaration that allows reassignment, but not declaration reassignment (i.e., it can't be declared twice). 3. **`var`**: A declaration that has function scope and can be reassigned. **Pros and Cons of Each Approach** 1. **`const`**: * Pros: Memory safety, performance benefits due to optimization by the JavaScript engine. * Cons: Reassignment is not allowed, which might require additional logic in code. 2. **`let`**: * Pros: Allows reassignment, suitable for functions that need to update variables. * Cons: Reassignment can lead to memory leaks if not managed properly. 3. **`var`**: * Pros: Wide compatibility and ease of use. * Cons: Potential performance issues due to variable hoisting and late binding. **Library and Special Features** None of the test cases explicitly use any libraries or special JavaScript features beyond standard syntax. **Benchmark Preparation Code** The provided `Script Preparation Code` is empty, which means that the benchmark assumes that no additional code is needed to prepare the script for execution. The `Html Preparation Code` is also empty. **Alternative Benchmarks** If you'd like to explore alternative benchmarks, here are a few examples: * `Array.prototype.push() vs Array.prototype.length`: This benchmark compares the performance of two common array methods. * `String concatenation vs template literals**: This benchmark tests the performance of string concatenation using the `+` operator versus template literals. * `DOM mutations vs DOM updates`: This benchmark evaluates the performance of different approaches to updating the Document Object Model (DOM). Keep in mind that these are just a few examples, and there are many other possible benchmarks depending on your specific interests and use cases. I hope this explanation helps you understand the provided benchmark!
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