Explain lexical scope in JavaScript

Lexical scope in JavaScript refers to the scope chain that is created by the placement of functions and variables in the code. When a function is defined, it creates a new scope, and any variables declared within that function are only accessible within that scope. However, if a function is defined within another function, it has access to the variables declared in the outer function's scope as well. This is known as closure. For example, consider the following code:

function outerFunction() {
  var outerVariable = "I am in outer function";

  function innerFunction() {
    var innerVariable = "I am in inner function";
    console.log(outerVariable); // "I am in outer function"
  }

  innerFunction();
}

outerFunction();

In this code, the innerFunction has access to the outerVariable declared in the outerFunction's scope, even though it is not declared within the innerFunction. This is because of lexical scoping. Lexical scope can also be used to create private variables and methods in JavaScript. By declaring variables and functions within a closure, they are not accessible outside of that closure, effectively making them private. This can be useful for encapsulating functionality and preventing it from being modified or accessed from outside the closure. Overall, understanding lexical scope is important for writing efficient and maintainable JavaScript code. By properly scoping variables and functions, we can avoid naming conflicts and create more modular and reusable code.