What is the difference between var, let, and const in JavaScript?

Question

This question explores JavaScript and addresses practical considerations related to: What is the difference between var, let, and const in JavaScript?

Q&A Network · Accepted Answer

In JavaScript, "var", "let", and "const" are used for variable declarations, but they differ in scope, hoisting, and mutability. Here's a concise example to illustrate these differences:

// var is function-scoped and can be redeclared
        function varExample() {
            var x = 1;
            if (true) {
                var x = 2; // same variable
                console.log(x); // 2
            }
            console.log(x); // 2
        }

// let is block-scoped and cannot be redeclared in the same scope
        function letExample() {
            let y = 1;
            if (true) {
                let y = 2; // different variable
                console.log(y); // 2
            }
            console.log(y); // 1
        }

// const is block-scoped and cannot be reassigned
        function constExample() {
            const z = 1;
            if (true) {
                const z = 2; // different variable
                console.log(z); // 2
            }
            console.log(z); // 1
        }

varExample();
        letExample();
        constExample();

ADDITIONAL COMMENT:
- "var" is function-scoped, meaning it is accessible throughout the function in which it is declared, and it can be redeclared.
- "let" is block-scoped, meaning it is only accessible within the block it is declared in, and it cannot be redeclared in the same scope.
- "const" is also block-scoped like "let", but it cannot be reassigned after its initial assignment.
- Use "let" and "const" for better code clarity and to avoid issues with variable redeclaration and scope.

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What is the difference between var, let, and const in JavaScript?

Asked on May 13, 2026

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