let
The 'let' keyword is a variable declaration in JavaScript (and other languages like TypeScript) that creates a block-scoped variable, meaning it is only accessible within the block, statement, or expression where it is defined. It was introduced in ECMAScript 6 (ES6) to address issues with the older 'var' keyword, such as hoisting and global scope leakage. Unlike 'var', 'let' variables are not initialized until their definition is evaluated, preventing access before declaration.
Developers should use 'let' when they need variables that are limited to a specific block scope, such as within loops, conditionals, or functions, to avoid unintended side effects and improve code clarity. It is particularly useful in modern JavaScript development for managing state in loops, preventing variable redeclaration errors, and adhering to best practices in ES6+ codebases. Use 'let' instead of 'var' for most variable declarations to enforce stricter scoping rules and reduce bugs.