The Number Type in TypeScript

In TypeScript, the number type is used to represent numbers, both integers and floating-point.

Unlike other languages that may have distinct types for integers and floating-point numbers, TypeScript (and JavaScript) uses a single number type for both.

let integer: number = 42;
let decimal: number = 3.14;
let hex: number = 0xff;    // Hexadecimal notation
let bin: number = 0b1010;  // Binary notation
let oct: number = 0o744;   // Octal notation

TypeScript also supports scientific notation for representing very large or very small numbers.

let large: number = 1e6;      // 1 * 10^6
let small: number = 1e-6;     // 1 * 10^-6

Arithmetic Operations

TypeScript allows performing basic arithmetic operations with the number type: addition, subtraction, multiplication, division, and modulus.

let a: number = 10;
let b: number = 3;

console.log(a + b);  // 13
console.log(a - b);  // 7
console.log(a * b);  // 30
console.log(a / b);  // 3.3333333333333335
console.log(a % b);  // 1

Precision and Rounding Errors

Since TypeScript uses JavaScript’s number type, which is based on the IEEE 754 standard for floating-point numbers, there can be precision issues in operations with decimal numbers.

let x: number = 0.1 + 0.2;
console.log(x);  // 0.30000000000000004

Methods and Properties of Number

TypeScript provides several static methods and properties on the Number object to help us work with numbers.

Static Properties

• Number.MAX_VALUE: The maximum representable numeric value.
• Number.MIN_VALUE: The smallest positive representable numeric value.
• Number.POSITIVE_INFINITY: Represents positive infinity.
• Number.NEGATIVE_INFINITY: Represents negative infinity.
• Number.NaN: Represents a value that is not a number (Not-A-Number).

console.log(Number.MAX_VALUE);  // 1.7976931348623157e+308
console.log(Number.MIN_VALUE);  // 5e-324
console.log(Number.POSITIVE_INFINITY);  // Infinity
console.log(Number.NEGATIVE_INFINITY);  // -Infinity
console.log(Number.NaN);  // NaN

Static Methods

• Number.isFinite(value): Determines whether the value is a finite number.
• Number.isInteger(value): Determines whether the value is an integer.
• Number.isNaN(value): Determines whether the value is NaN.
• Number.isSafeInteger(value): Determines whether the value is a safe integer (between -(2^53 - 1) and 2^53 - 1).

console.log(Number.isFinite(123));  // true
console.log(Number.isInteger(123.456));  // false
console.log(Number.isNaN(NaN));  // true
console.log(Number.isSafeInteger(Math.pow(2, 53)));  // false

Type Conversion

String to Number Conversion

It is common to need to convert strings to numbers. TypeScript provides several ways to do this, including parseInt, parseFloat, and the unary + operator.

let string: string = "42";
let integer: number = parseInt(string);  // 42
let float: number = parseFloat("3.14");  // 3.14
let number: number = +string;  // 42

Number to String Conversion

To convert a number to a string, the toString method can be used.

let num: number = 42;
let str: string = num.toString();  // "42"

Handling Special Numbers

NaN (Not-a-Number)

NaN is a special value that represents a non-numeric value. It is the result of undefined or illegal operations, such as dividing 0 by 0.

let nan: number = 0 / 0;
console.log(nan);  // NaN
console.log(isNaN(nan));  // true

Infinity

The Infinity value occurs when a numerical operation exceeds the maximum representable range.

let infinity: number = 1 / 0;
console.log(infinity);  // Infinity