Do `let` and `const` Variables Exhibit Hoisting in JavaScript?

"Are Variables Declared with Let or Const Hoisted?"

Hoisting in JavaScript

In JavaScript, hoisting is a mechanism that moves variable declarations to the top of their scope. Traditionally, variables declared with the var keyword are hoisted, meaning they can be accessed before they are declared.

Hoisting with Let and Const

However, variables declared with the let and const keywords exhibit different behavior when it comes to hoisting. While they are still considered hoisted, they have some unique limitations:

• ReferenceError: Attempts to access a let or const variable before it is declared result in a ReferenceError. This is in contrast to var variables, which return undefined when accessed before declaration.
• Temporal Dead Zone: For let and const variables, there exists a "temporal dead zone" between the declaration and initialization. During this period, accessing the variable will cause a ReferenceError.

Differences Between Let and Const

While both let and const declarations are subject to hoisting and have temporal dead zones, there is a key difference between them:

• Assignment: Let variables can be reassigned to a different value, while const variables cannot be reassigned after initialization.

Summary

All declarations (var, let, const, function, function*, class) are hoisted in JavaScript. However, let and const variables have a temporal dead zone during which they cannot be accessed. This behavior ensures that variables are initialized before they are used, reducing the risk of runtime errors. The only difference between let and const in this regard is that const variables cannot be reassigned.

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