Today, lexical scope is the norm: free variables are evaluated considering the environment where the function is defined. Lexical scope complicates the implementation of languages with first-class functions, because it requires the support of closures. On the other hand, lexical scope makes source code easier to read. Most languages invented since Algol have lexical scope. One notable exception is JavaScript, where the special variable this is confusing because it can be lexically or dynamically scoped, depending on how the code is written.
