Lexical Scope in JavaScript: How Code Structure Determines Variable Access

Lexical scope is a JavaScript rule that determines where a variable can be accessed based on where the code is written, not where it is called from. Functions can access variables from their outer scopes, a concept extended by nested scopes where inner functions can reach outer variables but not vice versa. Block scope, created using let and const within curly braces, also follows this lexical scoping system. While lexical scope defines the rules of variable accessibility, a lexical environment is the internal mechanism JavaScript uses to track variables and their connections to outer scopes. Grasping lexical scope is foundational to understanding closures, which allow functions to retain access to variables from their surrounding scope even after the outer function has completed execution.