Volva NPM | npm.io

Vǫlva

Easier type checks for JS/TS variables. To replace avant-garde spellcasting like typeof yourVariable === 'object' && yourVariable !== null with easier semantics.

Motivation

Type checking with javascript can be inconsistent. typeof yourVariable tells only half of the story. It does not recognize arrays from objects, it doesn't differentiate integers from floats or nulls from objects. Then you have to remember behind which API the right check was hidden. Not to mention more exact types, like integers or floats.

Vǫlva hides these inconsistensies behind simple-to-remember API with comprehensive test suite.

Install

yarn add volva

Usage

Vǫlva gives "isX" syntax for common js types. isArray, isObject, isString, isBoolean etc.

import {
  isArray,
  isBigInt,
  isBoolean,
  isFloat,
  isFunction,
  isInteger,
  isMap,
  isNumber,
  isObject,
  isSet,
  isString,
  isSymbol,
} from 'volva';


console.log(isArray( [1,2,3,4] ) ); // True.
console.log(isArray( {} ) ); // False.

console.log(isBoolean( false ) ); // True.
console.log(isBoolean( 'true' ) ); // False.

console.log(isFloat( 30.7 ) ); // True.
console.log(isFloat( 30 ) ); // False.

console.log(isInteger( 30 ) ); // True.
console.log(isInteger( 30.7 ) ); // False.

console.log(isNumber( 666 ) ); // True.
console.log(isNumber( 'Number' ) ); // False.

console.log(isObject( { title: 'Bone Silence', author: 'Alastair Reynolds' } ) ); // True.
console.log(isObject( [1,2,3,4] ) ); // False.

console.log(isString( 'I was forced to speak, now silence is my name' ) ); // True.
console.log(isString( 1917 ) ); // False.

TypeScript usage.

Since v2.0.0 Vǫlva has been written in TypeScript. TypeScript should understand Vǫlvas type-checks with type predicates. So if you use function like if(isString(yourVariable)), TypeScript compiler should understand we're dealing with string variable.

Additional help for odd cases.

On top of individual type checks, Vǫlva provides getType() for getting exact info. Whereas typeof may treat all numbers as just "number" or all objects, arrays and nulls as objects, getType() tells you exactly what you're dealing with.

Added types are integer, float and array etc.

import { getType } from 'volva';

const myInteger = 12345;
console.log( getType(myInteger) ); // integer.

const myFloat = 353.4644;
console.log( getType(myFloat) ); // float.

const myArray = [ 'Revenger', 'Shadow Captain', 'Bone Silence' ];
console.log( getType(myArray) ); // array.

const myObject = {};
console.log( getType(myObject) ); // object.

const myBool = true;
console.log( getType(myBool) ); // boolean.

const myString = 'Far away on the other side, will you come to talk to me this night';
console.log( getType(myString) ); // string.