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JavaScript Variables (`let` & `const`) Explained

JavaScript introduced let and const to provide clearer and safer ways to declare variables compared to the legacy var keyword.

Using `let`

Purpose: For values that may change over time.
Scope: Block-scoped (only exists inside the nearest {} block).

let count = 5;         // initial value
count = 10;            // update later
console.log(count);    // Outputs: 10

Key Points for `let`:

Prevents accidental global variables.
No hoisting surprises—you can’t use it before declaration.

Using `const`

Purpose: For values that should remain constant.
Scope: Block-scoped (same as let).

const pi = 3.14;       // fixed value
// pi = 3.14159;      // Error! Cannot reassign a const
console.log(pi);       // Outputs: 3.14

Key Points for `const`:

Guarantees the variable won’t be reassigned.
Encourages safer, more predictable code.

Recommendation:

Use const by default for any variable that doesn’t need reassignment.
Use let when you know the value will change.
Together, let and const help you write clearer, more maintainable JavaScript.

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Variables using the "var" keyword

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Variables with "const" and "let" keywords

A quick overview of when and how to use let and const in modern JavaScript. JavaScript introduced let and const to provide clearer and safer ways to declare variables compared to the legacy var keyword.

3m 48s