JavaScript’s Data Type Questions #3

Hi Friends!

Kamon acho!

Q: What does it mean that JavaScript is dynamically typed?

Ans: In JavaScript, you can assign a value of one type to a variable and later assign a different type.

let name = "Padmanava";  
name = 42; // No error

Number & BigInt

Q: What is the safe integer range in JavaScript?

Ans: JavaScript’s Number type has a safe range from -(2^53 - 1) to (2^53 - 1).

If you need larger numbers, use BigInt.

let bigNum = 9007199254740991n; // BigInt

NaN (Not-a-Number)

Q: What happens when you perform arithmetic with NaN?

Ans: Any arithmetic operation involving NaN results in NaN, except NaN ** 0, which is 1.

console.log(NaN + 5);  // NaN  
console.log(NaN * 2);  // NaN  
console.log(NaN / 2);  // NaN  
console.log(NaN ** 0); // 1

Template Literals ( )

Q: What makes template literals better than regular strings?

Ans: They allow multi-line strings, variable interpolation using ${}, and are more modern than "" or ''.

let name = "Padmanava";  
console.log(`Hello, ${name}!`); // "Hello, Padmanava!"

null vs undefined

Q: How are null and undefined different?

Ans: null is an intentional absence of a value, while undefined means a variable is declared but not assigned.

let a = null;  
let b;  
console.log(a); // null  
console.log(b); // undefined

Equality Operators (== vs ===)

Q: How does == differ from ===?

Ans: == compares values without checking types, while === checks both values and types.

console.log(5 == "5");  // true  (loose comparison)  
console.log(5 === "5"); // false (strict comparison)

🎭 The typeof Operator

Q: What is the result of typeof null?

Ans: It returns "object" due to an old JavaScript bug that was never fixed.

console.log(typeof null); // "object"

Boolean Conversion in Arithmetic

Q: How do true and false behave in arithmetic?

Ans: true → 1 and false → 0.

console.log(5 + true);  // 6  (true → 1)  
console.log(5 - false); // 5  (false → 0)  
console.log(true + true); // 2

String & Number Operations

Q: When does + perform concatenation instead of addition?

Ans: If at least one operand is a string, + concatenates. Otherwise, it performs addition.

console.log(5 + "5"); // "55" (string concatenation)  
console.log(5 - "5"); // 0 (number subtraction)

null and undefined in Arithmetic

Q: How do null and undefined behave in arithmetic?

Ans: null converts to 0, while undefined converts to NaN.

console.log(5 + null); // 5  (null → 0)  
console.log(5 + undefined); // NaN (undefined → NaN)

Final Takeaways

✔ JavaScript is dynamically typed, meaning variable types can change.
✔ null is intentional emptiness, undefined means uninitialized.
✔ == checks values, === checks values and types.
✔ NaN propagates in math, but NaN ** 0 === 1.
✔ typeof null === "object" is an old JavaScript quirk.
✔ + concatenates if a string is involved, otherwise it performs addition.
✔ Boolean values convert to numbers in arithmetic (true → 1, false → 0).