What is lexical scope and how does it differ in various programming languages?

What is lexical scope and how does it differ in various programming languages?

Lexical scope refers to the visibility of variables in nested functions. In languages like JavaScript, a variable defined in a function is accessible only within that function and its nested functions. In contrast, languages like Python also use lexical scoping but have different rules for closures.

Can you give me an example of lexical scope in JavaScript?

Sure! In JavaScript, if you define a variable inside a function, it cannot be accessed outside of that function. For example:

function outer() {
    let outerVar = 'I am outside!';
    function inner() {
        console.log(outerVar); // This will log 'I am outside!'
    }
    inner();
}
outer();

How does lexical scope work in Python?

In Python, lexical scope works similarly. A variable defined in a function is not accessible outside of it. For example:

def outer():
    outer_var = 'I am outside!'
    def inner():
        print(outer_var)  # This will print 'I am outside!'
    inner()
outer()

Are there any languages that don't use lexical scope?

Yes, some languages, like older versions of BASIC, use dynamic scoping instead of lexical scoping. In dynamic scoping, a variable's value is determined by the calling context, not the location of the variable declaration.