Benchmark: var vs let vs const init

Tests:

var
var nums = 55;
let
let nums = 56;
const
const nums = 57;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
var
let
const

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 months ago)

User agent: Mozilla/5.0 (Linux; Android 10; HITV102C Build/QP1A.190711.020; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/89.0.4389.72 MQQBrowser/6.2 TBS/046295 Mobile Safari/537.36 WPS/st=android-mobile&bt=webview&sv=29&bv=89&cn=android-iciba

Browser/OS: QQ Browser Mobile 6 on Android

View result in a separate tab

Test name	Executions per second
var	510555648.0 Ops/sec
let	512052960.0 Ops/sec
const	507099840.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks!

**What is being tested?**

The provided JSON represents a benchmarking test case that compares the performance of three different variable declaration statements in JavaScript: `var`, `let`, and `const`. The test is designed to measure the execution speed of assigning a value to each type of variable.

**Options compared:**

*   `var`: A function-scoped, non-block-scoped variable declaration. Variables declared with `var` are not hoisted, but their assignments can be.
*   `let`: A block-scoped variable declaration. Variables declared with `let` are hoisted to the top of their scope, and their assignment is also hoisted.
*   `const`: A block-scoped constant variable declaration. Variables declared with `const` are also hoisted, but they cannot be reassigned.

**Pros and Cons:**

*   **Var**: Pros:
    *   Faster execution speed due to non-block scoping
    *   Less memory usage compared to `let` and `const`
    *   Can be used for function scope variables (though not recommended)
    Cons:
    *   Non-block scoping can lead to unexpected behavior in certain situations
    *   Variables are not hoisted, which can cause errors if used before assignment
*   **Let**: Pros:
    *   Block-scoped, which improves code readability and maintainability
    *   Allows for use of `let` with `for`, `while`, and `if` loops without issues
    Cons:
    *   Slower execution speed due to block scoping
    *   Variables are hoisted to the top of their scope, but not initialized
*   **Const**: Pros:
    *   Block-scoped constant variables, which improve code readability and maintainability
    *   Prevents accidental reassignment, making it easier to predict program behavior

**Library:**

There is no explicit library mentioned in the provided JSON. However, if you're interested in testing JavaScript performance with libraries like `Benchmark.js` or `jsbench`, you can consider using them.

**Special JS feature/syntax:**

The test doesn't use any special JavaScript features or syntax. It's a straightforward comparison of three variable declaration statements.

**Other alternatives:**

If you want to explore other benchmarking tools for JavaScript, some popular alternatives include:

*   `Benchmark.js`
*   `jsbench`
*   `Google Benchmark`

Keep in mind that each tool has its strengths and weaknesses, so be sure to choose the one that best suits your needs.

Related benchmarks:

var vs let vs const init (version: 0)

Comparing performance of: var vs let vs const

Created: 5 years ago by: Guest

Jump to the latest result

var

let

const

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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