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Itamar Tati
Itamar Tati

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Understanding the Difference Between let, const, and var in JavaScript (1 Minute Guide)

When working with JavaScript, you'll encounter three ways to declare variables: let, const, and var. While they all serve the same purpose, they behave differently in terms of scoping, mutability, and hoisting. Let's break it down quickly:

  1. let:

    • Block-scoped: Meaning it only exists within the nearest block (like a loop or an if statement).
    • Mutable: The value of a variable declared with let can be reassigned.
  2. const:

    • Block-scoped like let.
    • Immutable: Once a variable is assigned a value with const, it cannot be reassigned. However, note that the contents of objects or arrays declared with const can still be modified.
  3. var:

    • Function-scoped: Unlike let and const, var is scoped to the nearest function block, or global if declared outside of a function.
    • Hoisted: Variables declared with var are moved to the top of their scope during compilation, potentially leading to unexpected results.

Which one should you use?

  • Use let when you need to reassign values.
  • Use const by default for values that shouldn’t change.
  • Avoid var unless you’re dealing with legacy code.

By understanding the nuances of these keywords, you can write cleaner and more predictable code in JavaScript.

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