Question

Assume the following JavaScript program was interpreted using static-scoping rules. What value of x is displayed in function sub1? Under dynamic-scoping rules, what value of x is displayed in function sub1?

var x;
function  sub1() {
  document.write("x = " + x + "");
}
function  sub2() {
   var x;
   x = 10;
   sub1();
}
x = 5;
sub2();

Answer 1

Using Static Scoping rules:

• In static scoping, the variable will be always referred to the top-level environment. With the help of the static scoping, it becomes very easy to develop a modular code and also figure out the scope just by analyzing the code.
• So, looking at the above function it is clear that while running the code by looking at the static scoping rules it will display X = 5.
• The reason behind it is simply because this represents the global value of x which is the top-level environment of the variable that the local assignment inside the function.

Using Dynamic Scoping rules:

• In dynamic scoping, the variable will refer to the most recent assignment to the global identifier and will consider each of the identifier with the global stack of the bindings and the occurrence of the identifiers that are being searched and managed in the most recent binding.
• Hence, in simpler terms, it will display x = 10 as it is later on assigned inside the function changing the global value of x and then will refer to the value assigned by the function.
• Hence, dynamic scoping makes the code tougher to read but has many use cases in the modern programming languages and is actively used as it helps in saving memory spaces.

Hence, these are the output of the programs according to the different scopes suggested.