Benchmark: const vs let vs var vs sloppy v3

Tests:

var
var nagg = new Map(); function send_nodeagg(aggr) {return aggr}; var nodeagg = {aggr: nagg, send: send_nodeagg, currdt: '', currhost: '', currmap: new Map()}; nodeagg.send(nodeagg.aggr);
let
let nagg = new Map(); let send_nodeagg = (aggr) => {return aggr}; let nodeagg = {aggr: nagg, send: send_nodeagg, currdt: '', currhost: '', currmap: new Map()}; nodeagg.send(nodeagg.aggr);
const
const nagg = new Map(); const send_nodeagg = (aggr) => {return aggr}; const nodeagg = {aggr: nagg, send: send_nodeagg, currdt: '', currhost: '', currmap: new Map()}; nodeagg.send(nodeagg.aggr);
sloppy
nagg = new Map(); function send_nodeagg(aggr) {return aggr}; nodeagg = {aggr: nagg, send: send_nodeagg, currdt: '', currhost: '', currmap: new Map()}; nodeagg.send(nodeagg.aggr);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
var
let
const
sloppy

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36

Browser/OS: Chrome 118 on Linux

View result in a separate tab

let

4.9M/s

const

4.9M/s

var

4.9M/s

sloppy

1.4M/s

View exact numbers

Test name	Executions per second
✓ let	4,949,294 Ops/sec
const	4,930,474 Ops/sec
var	4,921,383 Ops/sec
sloppy	1,402,872 Ops/sec

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

LLMs can make mistakes. Check important info.

Measuring the performance of JavaScript variables and functions is crucial to understand how different approaches impact execution speed.

The provided benchmark defines four test cases:

1.  `var`: The variable declaration uses the traditional `var` keyword, which has function scope and is hoisted to the top of its surrounding block.
2.  `let`: The variable declaration uses the modern `let` keyword, which also has function scope but does not get hoisted like `var`.
3.  `const`: Similar to `let`, `const` declares a constant value that cannot be reassigned, with function scope and no hoisting.
4.  `sloppy v3`: This is an older style of variable declaration in JavaScript, using the old syntax for variable declarations without block scope.

**Comparison Options**

The test cases are designed to compare the execution speed of each approach:

*   **Hoisting**: The position of variable declarations and assignments relative to their usage. `var` and `let` get hoisted, while `const` does not.
*   **Block Scope**: The visibility and accessibility of variables within blocks (e.g., if statements or loops). All four approaches have block scope, but `sloppy v3` uses a syntax that is less readable.

**Pros and Cons**

Here are the pros and cons of each approach:

*   **Hoisting**: 
    *   Pros: Easier to read and write code, especially for older JavaScript versions.
    *   Cons:
        *   Potential issues with variable shadowing or unexpected behavior due to hoisted variables being accessed before they're declared.
        *   Less explicit about the scope of a variable.
*   **Block Scope** (using `let` and `const`):
    *   Pros: Provides clear, explicit block scope, reducing potential issues with variable shadowing.
    *   Cons:
        *   May require additional semicolons to ensure proper syntax highlighting or parsing in older browsers/ IDEs.
        *   Less readable than traditional `var` for some developers, especially those used to `var`.
*   **Sloppy v3** (older style of variable declaration without block scope):
    *   Pros: Easier to read and write code when working with old JavaScript versions or very beginner-friendly.
    *   Cons:
        *   Less readable for most modern developers.
        *   Potential issues with variable shadowing due to lack of block scope.

**Library Usage**

There are no libraries used in the provided benchmark. The test cases only involve built-in JavaScript features.

**Special JS Features or Syntax**

There is an older syntax (`sloppy v3`) that uses `=` for variable declarations, which is less readable and can lead to errors when working with modern JavaScript versions. This is an older style of variable declaration without block scope, typically used in very old JavaScript versions (pre ES6) or certain legacy projects.

**Alternatives**

If you're interested in exploring alternatives or more comprehensive benchmarks, consider the following resources:

*   **Benchmarking libraries**: BenchmarkJS, fast-bench, and jsperf.
*   **JavaScript performance testing frameworks**: jsPerf, Benchmark.js, and perf.js.
*   **ES6+ syntax variations**: If you want to explore modern JavaScript features like classes, async/await, or arrow functions, you can experiment with these using popular compilers like Babel.

By understanding the differences in variable declarations and their execution speed, developers can make informed decisions about which approach best suits their specific use cases.

const vs let vs var vs sloppy v3 (version: 0) Benchmark.js

Comparing performance of: `var vs let vs const vs sloppy`

Created: 2 years ago by: Guest

Go to the latest result

var

let

const

sloppy

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

const vs let vs var vs sloppy v3 (version: 0) Benchmark.js

Comparing performance of: var vs let vs const vs sloppy

Created: 2 years ago by: Guest

Go to the latest result

var

let

const

sloppy

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: `var vs let vs const vs sloppy`