JavaScript: Comparisons and Conditionals

Question 1

How does the Undefined Data Type interact with Comparisons?

Answer 1

A variable is undefined when it has been declared but hasn’t been assigned a value. It’s the default value of uninitialized variables and function parameters that weren’t provided an argument. undefined converts to NaN in numeric contexts, which makes all numeric comparisons with undefined return false.
console.log(undefined > 0); // false
console.log(undefined < 0); // false
console.log(undefined == 0); // false

Question 2

How does the Null Data Type interact with Comparisons?

Answer 2

The null type represents the intentional absence of a value. When using the equality operator, null and undefined are considered equal. However, when using the strict equality operator (===), which checks both value and type without performing type coercion, null and undefined are not equal:
console.log(null == undefined); // true
console.log(null === undefined); // false

Question 3

What is a Switch Statement?

Answer 3

A switch statement evaluates an expression and matches its value against a series of case clauses. When a match is found, the code block associated with that case is executed. A break statement should be placed at the end of each case, to terminate its execution and continue with the next. The default case is an optional case and only executes if none of the other cases match. The default case is placed at the end of a switch statement.
const dayOfWeek = 3;

switch (dayOfWeek) {
case 1:
console.log(“It’s Monday! Time to start the week strong.”);
break;
case 2:
console.log(“It’s Tuesday! Keep the momentum going.”);
break;
case 3:
console.log(“It’s Wednesday! We’re halfway there.”);
break;
case 4:
console.log(“It’s Thursday! Almost the weekend.”);
break;
case 5:
console.log(“It’s Friday! The weekend is near.”);
break;
case 6:
console.log(“It’s Saturday! Enjoy your weekend.”);
break;
case 7:
console.log(“It’s Sunday! Rest and recharge.”);
break;
default:
console.log(“Invalid day! Please enter a number between 1 and 7.”);
}