The number type in TypeScript.

In TypeScript, number is a primitive type that can hold all kinds of numbers including integers, floats, hexadecimal, binary, octal, and scientific notation.

let age: number = 25;
let price: number = 99.99;

Usage in TypeScript with type annotation:

let score: number = 90;
let height: number = 5.9;
let hex: number = 0xff;

Useful Number Methods:
toFixed()
Rounds the number to a fixed number of decimal places:

let pi = 3.14159;
console.log(pi.toFixed(2)); // "3.14"

toExponential():
Converts to scientific notation:

let big = 123456;
console.log(big.toExponential()); // "1.23456e+5"

toString(radix):
Converts number to string in specified base:

let num = 255;
console.log(num.toString(16)); // "ff"
console.log(num.toString(2));  // "11111111"

Type Guarding:
Ensure type safety when using number | string:

function double(x: number | string) {
  if (typeof x === "number") {
    return x * 2;
  }
  return parseFloat(x) * 2;
}

Special Numeric Values:

let a = 1 / 0;          // Infinity
let b = -1 / 0;         // -Infinity
let c = parseInt("abc"); // NaN (Not a Number)

You should always check for isNaN() when doing conversions.

Math Library Functions:

Math.round(3.6);   // 4
Math.floor(3.9);   // 3
Math.ceil(3.1);    // 4
Math.abs(-10);     // 10
Math.pow(2, 3);    // 8
Math.sqrt(16);     // 4
Math.random();     // Random number between 0 and 1

Using Enums with Numbers:

enum Size {
  Small = 1,
  Medium = 2,
  Large = 3
}

let selected: Size = Size.Medium;

Enums are great when you need readable numeric identifiers.

Custom Type Guard:

function isNumber(val: unknown): val is number {
  return typeof val === "number" && !isNaN(val);
}

Number() constructor বা wrapper:
In JavaScript/TypeScript, the Number() function is used to convert other types (like strings or booleans) to a number. It can also be used as a wrapper object, though this is less common and generally discouraged.

let n = new Number(5);  // object wrapper (not primitive)
typeof n; // "object"

isNaN() vs Number.isNaN()
New developers often don't know the difference between the global isNaN() function and Number.isNaN(). It would be good to mention this.

isNaN("abc"):; // true (coerces to NaN)
Number.isNaN("abc"); // false (doesn't coerce)

Number parsing functions:
Mentioning the Number() function alongside parseInt() and parseFloat() increases completeness.

Number("123.45"); // 123.45

Type narrowing with isFinite():
When dealing with scientific or dynamic values, isFinite() becomes helpful.

Number.isFinite(Infinity); // false

Comments

[Mohammad Hasibul Hasan]

Thanks for clearing the concept, I was a little confused...