The difference between let, var, and const in JavaScript pertains to their scope, hoisting behavior, and mutability:
var:
Scope: Function-scoped. If declared inside a function, it is accessible throughout the function. If declared outside any function, it is globally scoped.
Hoisting: Variables declared with var are hoisted to the top of their scope and initialized with undefined.
Re-declaration: You can re-declare var variables within the same scope.
let:
Scope: Block-scoped. It is only accessible within the block (enclosed by {}) where it is defined.
Hoisting: Variables declared with let are hoisted but not initialized. Accessing them before declaration results in a ReferenceError.
Re-declaration: You cannot re-declare let variables within the same scope.
const:
const:
Scope: Block-scoped, similar to let.
Hoisting: Variables declared with const are hoisted but not initialized. Accessing them before declaration results in a ReferenceError.
Re-declaration: You cannot re-declare const variables within the same scope.
Mutability: The variable identifier cannot be reassigned, but if the variable is an object or array, the contents can be changed.