JavaScript Integer

In JavaScript, an Integer is a whole number without any decimals. It can be positive, negative, or zero. Integers are widely used in programming for counting, indexing, loops, and arithmetic operations. Although JavaScript treats all numbers as Number type, integers have specific properties and common use cases.

Key Points:

• An integer is a whole number (without a decimal part).
• It can be positive, negative, or zero.
• JavaScript uses the same type for integers and floats (Number).
• For very large integers, BigInt is used.
• Integers are commonly used in loops, counters, and array indexing.

1. Integer Examples in JS

let age = 25;          // positive integer
let temperature = -5;  // negative integer
let count = 0;         // zero
console.log(typeof age); // "number"

2. Integer Properties in JS

• Safe Integer Range: Number.MAX_SAFE_INTEGER → 9007199254740991
• Number.MIN_SAFE_INTEGER → -9007199254740991
• Numbers outside this range may lose precision.
• BigInt: Used for integers larger than safe range. Example: let bigNum = 123456789012345678901234567890n;

3. Arithmetic Operations

let a = 10;
let b = 3;

console.log(a + b); // 13
console.log(a - b); // 7
console.log(a * b); // 30
console.log(a / b); // 3.3333333333333335 (float result)
console.log(a % b); // 1  (modulus)
console.log(a ** b); // 1000 (exponentiation)

4. Increment & Decrement

let x = 5;
x++;   // x = 6
x--;   // x = 5

5. Unary Plus / Minus

let y = "10";
let z = +y;  // converts string "10" to number 10
console.log(typeof z); // "number"

6. Integer Checking Methods

• Number.isInteger(value) – checks if a value is an integer
• Math.floor(value) – converts number to nearest lower integer
• Math.ceil(value) – converts number to nearest higher integer
• Math.round(value) – rounds number to nearest integer
• parseInt(string) – converts string to integer

console.log(Number.isInteger(10));   // true
console.log(Number.isInteger(10.5)); // false

console.log(Math.floor(10.7)); // 10
console.log(Math.ceil(10.3));  // 11
console.log(Math.round(10.5)); // 11

let str = "123";
let num = parseInt(str);
console.log(num); // 123

7. BigInt for Large Integers

let bigNum = 123456789012345678901234567890n;
console.log(typeof bigNum); // "bigint"

8. Integer vs Float Comparison

Feature	Integer	Float
Decimal part	None	Exists
Type in JS	Number	Number
Examples	5, -10, 0	3.14, -5.5
Operations	+ - * / % **	+ - * /
Precision	Exact (within safe range)	Approximate (due to decimals)

9. Real-life Usage

• Counting items in a list: cart.length
• Loop iteration: for(let i = 0; i < 10; i++) { }
• Age, marks, temperature, scores
• Flags: 0 = false, 1 = true
• Array indexing: arr[0], arr[1]

10. Tips & Notes

• In JavaScript, integer and float share the same type, but usage and operations differ.
• Division may produce a float; for exact integer, use Math.floor() or Math.round().
• For very large numbers, using BigInt is safe.
• Always remember Number.isInteger() for programming and exams.
• Integers form the base of programming – widely used in loops, counters, indexes, and calculations.