let const
let and const are block-scoped variable declarations introduced in ECMAScript 6 (ES6) for JavaScript. They provide more predictable scoping behavior compared to var, with let allowing reassignment and const enforcing immutability for primitive values and reference stability for objects. These declarations help prevent common bugs like variable hoisting issues and accidental reassignments.
Developers should use let and const in modern JavaScript projects to write cleaner, more maintainable code with explicit scoping. Use let for variables that need reassignment (e.g., loop counters or state updates) and const for values that should not be reassigned (e.g., configuration constants or function references). This practice enhances code readability and reduces errors in applications like web apps, Node.js servers, and frameworks like React or Vue.