JavaScript Data Types: Primitive & Non-Primitive

Why is it Used?

• Ensures proper operations on values
• Helps in memory management
• Avoids runtime errors

1. Number

The Number data type in JavaScript is a primitive type used to store numeric values, including integers and floating-point numbers. Example : 7, 0, -7, 2.8, -8.5, Infinity, -Infinity, NaN

// All of the following variables contains Number data-type
const a =  7
const b = 0
const c = -7
const d = 2.8
const e = -8.5
const f = Infinity
const g = -Infinity
const h = NaN

// Copy behaviour 
let num1 = 7;
let num2 = num1; // Copy of value, not reference
num1 = 10;
console.log(num2); // 7 (remains unchanged)

// Stored in stack as a fixed-size value.
// Copying a number creates a separate memory space.

2. BigInt

BigInt is a primitive data type in JavaScript that allows the representation of integers larger than Number.MAX_SAFE_INTEGER (2^53 - 1) without losing precision. It is mainly used for arbitrary-precision arithmetic, cryptography, and precise financial calculations.

A BigInt is created by adding n at the end of an integer or by using the BigInt() function.

let big1 = 123456789012345678901234567890n // Using "n" suffix
let big2 = BigInt(123456789012345678901234567890n)  // Using BigInt() constructor

• The exact storage format depends on the JavaScript engine
• It is not stored directly in the stack due to its dynamic size.The stack contains a reference to the BigInt stored in the heap.
• BigInt has no predefined max/min limit, so it will keep growing as long as memory allows.if it grows too large then Memory overflow/Performance issues/Crashes may occure.
• Number, which follows IEEE 754 (64-bit floating-point), BigInt uses a variable-length representation for storing large numbers.

let big1 = BigInt(123456789012345678901234567890); // => 123456789012345677877719597056n
let big2 = BigInt("123456789012345678901234567890"); // => 123456789012345678901234567890n

Wait Wait Wait !!! , In above example values are looking similar but why they are storing different value in variable ??? In variable big1 in above example a Number data-type is passed to BigInt, if the number exceeds the MAX_SAFE_INTEGER then javascript rounds the number which leads to Precision Loss

(If you still havn't understood bigint, then assume bigint a only numeric string. operations can be performs between two bigint)

Best Practice : Always use a string when working with very large numbers in BigInt()

3. String

A string is a sequence of characters used to represent text in programming. In JavaScript (and many other languages), a string is immutable, meaning it cannot be changed after it's created. We can create a string using :

• Single quotes → 'Hello'
• Double quotes → "Hello"
• Backticks (template literals) → `Hello`

name1 = 'John'  // Using single quotes
name2 = " Doe"  // Using double quotes
name3 = `Bob`   // Using backticks
name4 = 'alice' 
name5 = `${name4} carlos` // interpolation Output: alice carlos

• Strings are stored in memory as a sequence of Unicode characters.
• Strings smaller than a certain size are stored into stack and bigger are stored into heap, the size limit depends upon browser and system memory
• Since string is immutable, if you want to modify a string then you have to create a new one instead of modifying the existing one.

let str = "Cyber";
str[0] = "X"; 
console.log(str); // "Cyber" (No change, because strings are immutable)

let str1 = "Hello";
let str2 = str1; // str2 points to the same "Hello" in memory
str1 = "World";  // A new "World" string is created; str2 is still "Hello"

4. Boolean

A Boolean is a data type that can only have two possible values :

1. false : In JavaScript, the following values are treated as falsy - false, 0, -0, 0n, "", null, undefined, NaN
2. true : Everything except the falsy values is truthy.

if ("hello") console.log("hello is true")    // gives output
if (0) console.log("0 is false")    // no output

• Stored in the stack as a single bit or byte (depending on optimization).

5. Undefined

undefined is a primitive data type in JavaScript that represents a variable that has been declared but not assigned a value.

• undefined means not assigned a value. JavaScript automatically assigns undefined to uninitialized variables.
• Objects & arrays return undefined for missing properties or indexes.
• Functions return undefined if no return statement is used.

let a
console.log(a)  // Output: undefined

let ary = [1,2,5] 
console.log(ary[5]) // Output: undefined

6. null

null is a primitive data type in JavaScript that represents intentional absence of a value. It is explicitly (& intentionally) set by the programmer

let x = null;
console.log(x); // Output: null

• BUG : JavaScript incorrectly treats null as an object due to a bug in early implementations.

7. Symbol

Comming soon .....