is-number

A lightweight, high-performance utility to check if a value is a number or can be converted to a number.

Installation

yarn add @alwatr/is-number
# or
npm install @alwatr/is-number

Usage

import {isNumber, toNumber, isFiniteNumber} from '@alwatr/is-number';

// Check if a value is a number
isNumber(123);       // true
isNumber('123');     // true
isNumber('abc');     // false

// Convert a value to a number if possible
toNumber(123);       // 123
toNumber('123');     // 123 
toNumber('abc');     // null

// Check if a value is a finite number (without type coercion)
isFiniteNumber(123); // true
isFiniteNumber(Infinity); // false
isFiniteNumber('123'); // false (no coercion)

API

isNumber(value: unknown): boolean

Checks if the value is a number or can be converted to a number.

toNumber(value: unknown): number | null

Converts the value to a number if possible, otherwise returns null.

isFiniteNumber(value: unknown): boolean

A cross-browser polyfill for Number.isFinite. Unlike the global isFinite, this doesn't coerce values to numbers before checking.

Why is this needed?

JavaScript type behavior can be confusing. This library helps to simplify number validation:

console.log(typeof '123');     // 'string'
console.log(+[]);              // 0
console.log(+'');              // 0
console.log(+'   ');           // 0
console.log(typeof NaN);       // 'number'
console.log(typeof Infinity);  // 'number'

isNumber Examples

Returns true

isNumber(5e3);               // true
isNumber(0xff);              // true
isNumber(-1.1);              // true
isNumber(0);                 // true
isNumber(1);                 // true
isNumber(1.1);               // true
isNumber('-1.1');            // true
isNumber('0');               // true
isNumber('0xff');            // true
isNumber('1');               // true
isNumber('1.1');             // true
isNumber('5e3');             // true
isNumber('012');             // true
isNumber(' 123 ');           // true

Returns false

isNumber(Infinity);          // false
isNumber(NaN);               // false
isNumber(null);              // false
isNumber(undefined);         // false
isNumber('');                // false
isNumber('   ');             // false
isNumber('foo');             // false
isNumber('123foo');          // false
isNumber([1]);               // false
isNumber([]);                // false
isNumber(function () {});    // false
isNumber({});                // false

toNumber Examples

Returns a number

toNumber(5e3);               // 5000
toNumber(0xff);              // 255
toNumber(-1.1);              // -1.1
toNumber(0);                 // 0
toNumber(1);                 // 1
toNumber('-1.1');            // -1.1
toNumber('0');               // 0
toNumber('0xff');            // 255
toNumber('5e3');             // 5000
toNumber(' 123 ');           // 123

Returns null

toNumber(Infinity);          // null
toNumber(NaN);               // null
toNumber(null);              // null
toNumber(undefined);         // null
toNumber('');                // null
toNumber('   ');             // null
toNumber('foo');             // null
toNumber('123foo');          // null
toNumber([1]);               // null
toNumber([]);                // null
toNumber(function () {});    // null
toNumber({});                // null

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Contributing

Contributions are welcome! Please read our contribution guidelines before submitting a pull request.