Understanding JavaScript Variable Hoisting and Function Scope

function test() {
  console.log(a);
  console.log(foo());

  var a = 1;
  function foo() {
    return 2;
  }
}

test();

Options:

A. undefined, undefined

B. ReferenceError

C. 1, 2

D. 2, undefined

Correct Answer: A. undefined, undefined

Explanation:

The correct answer is option A. undefined, undefined. This result can be understood by considering the concepts of variable hoisting and function scope in JavaScript.

In JavaScript, variables declared with the var keyword are hoisted to the top of their containing scope. However, they are not assigned a value during hoisting, resulting in an initial value of undefined. Similarly, function declarations are also hoisted, allowing them to be called before their actual declaration in the code.

In the given code snippet, the variable a and the function foo() are hoisted within the test() function scope. When console.log(a) is executed, a is declared but not yet assigned a value, leading to undefined being printed. Similarly, console.log(foo()) calls the foo() function, which returns 2 as expected.

Understanding hoisting and function scope is crucial in JavaScript to avoid unexpected results and ensure proper variable and function usage.