JavaScript Variable Declarations: var, let, const

While let, var, and const are all used to declare variables in JavaScript, there are some significant distinctions between them in terms of mutability, hoisting, and scoping.

Var:

Var declarations can be accessed across the entire function or script and are globally or function-scoped, which means they are not restricted to the block scope (enclosed within {}).
You can use variable names before they are declared in the code because during the compilation process, they are elevated to the top of their scope. But only the statements are exalted; their values are not.
It is possible to update and re-declare var variables.With the aid of QuillBot's paraphrasing tool, you may rapidly and effectively rework and reword your content!

For instance:

function exampleForVar() {
    if (true) {
        var x = 10;
    }
    console.log(x);  // Outputs 10, not blocked by the if statement
}

let:

Let declarations are only accessible inside the block (contained within {}) in which they are defined since they are block-scoped.
Allow variables to remain at the top of their respective blocks. Although they are raised, you are unable to access them prior to the announcement.
Variables cannot be re-declared in the same scope; they may only be reassigned.

For instance:

function exampleForLet() {
    if (true) {
        let y = 20;
        console.log(y);  // Outputs 20
    }
    // console.log(y);  // Error: y is not defined outside the block
}

const:

Block scope is also present in const declarations.
Const variables cannot have their values changed after they are declared; they must be initialized.
Const is not elevated to the top of its block like let is.

For instance:

function exampleForConst() {
    const z = 30;
    // z = 40;  // Error: Assignment to constant variable
    console.log(z);  // Outputs 30
}

For variable declarations, it's generally advised to use const by default and to use let only in situations when you know the variable's value will change. Because of its idiosyncrasies, var is used less often in current JavaScript; let and const are usually thought to be safer and more predictable.