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const vs let vs var fixed
(version: 0)
Comparing performance of:
var vs let vs const
Created:
2 years ago
by:
Guest
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Tests:
var
var g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()
let
let g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()
const
const g = { e: [] } g.o = function(x) { g.e.push(...[1,2,3]) } g.o()
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (3)
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Test case name
Result
var
let
const
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's dive into the world of JavaScript microbenchmarks. **What is being tested?** The provided JSON represents a benchmark that tests the performance difference between three variable declarations: `const`, `let`, and `var`. Each test case uses the same script, but with different variable declarations. **Options compared** The benchmark compares the performance of these three options: * `var`: The traditional way of declaring variables in JavaScript. Variables declared with `var` are function-scoped, which means they can be accessed from anywhere within a function. * `let`: Introduced in ECMAScript 2015 (ES6), `let` is a block-scoped variable declaration. This means that variables declared with `let` can only be accessed within the scope of the block or statement where it's declared. * `const`: Also introduced in ES6, `const` is used to declare immutable variables. Like `let`, variables declared with `const` are block-scoped. **Pros and Cons** * **Var**: + Pros: Has been the standard for a long time, widely supported by browsers and environments. + Cons: Can lead to unexpected behavior due to its function-scoping nature, making it harder to reason about code. * **Let**: + Pros: Improves code readability by clearly indicating block scope, reduces potential for variable pollution. + Cons: May require more explicit variable declarations, can be less familiar to developers without ES6 experience. * **Const**: + Pros: Makes the intent of a variable clear, reduces bugs due to unintentional mutation. + Cons: May seem restrictive or unnecessary for simple variables. **Library usage** There is no library mentioned in the provided benchmark definition. The script and HTML preparation codes are empty, suggesting that this benchmark focuses solely on the performance characteristics of `var`, `let`, and `const` declarations. **Special JavaScript features/syntax** The benchmark uses the `function` keyword to declare a function `o` with two parameters, `x`. No special syntax or features are used here. **Other alternatives** If you're interested in exploring more alternatives or variants of variable declarations, consider looking into: * `let const`: This is an experimental feature in some browsers and environments that combines the benefits of both `let` and `const`. * Dynamic variables (e.g., using `var foo = bar;`). These can lead to performance issues due to hoisting. * Hoisted variables (e.g., declaring a variable without initialization). This behavior can be surprising for developers. When working with JavaScript, it's essential to consider the trade-offs between different approaches and understand how they impact code readability, maintainability, and performance. The provided benchmark helps demonstrate the benefits of using `let` and `const` declarations in modern JavaScript development.
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