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typescript-tipo-number

The Number Type in TypeScript

  • 3 min
  • Beginner

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
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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
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Arithmetic Operations

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

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
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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
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To handle precision, especially in financial applications, it is common to use libraries like decimal.js or big.js

Number Methods and Properties

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.
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
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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
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Type Conversion

String to Number Conversion

It’s 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
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Number to String Conversion

To convert a number to a string, you can use the toString method.

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

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

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