2

“2”: The Type Conversion Library

A Node.js module for converting between various JavaScript types: arrays, iterators, maps, numbers, objects, and strings.

const {toArray, toIterator, toMap, toNumber, toObject, toString} = require('2')

let data = {a: 1, b: 2}
data = toMap(data)
data = toArray(data)
data = toObject(data)
data = toIterator(data)
data = toArray(data)
data = toMap(data)
data = toObject(data) // {a: 1, b: 2}

data = '1.23'
data = toNumber(data)
data = toString(data) // '1.23'

Installation

npm install 2 --save

Usage

Requiring the Functions

You can require needed functions via a destructuring assignment:

const {toArray, toIterator, toMap, toNumber, toObject, toString} = require('2')

Or you can require individual functions via submodules:

const toArray = require('2/array')
const toIterator = require('2/iterator')
const toMap = require('2/map')
const toNumber = require('2/number')
const toObject = require('2/object')
const toString = require('2/string')

Converting to Arrays

const toArray = require('2/array')

// Map => Array
let map = new Map()
map.set('a', 1)
map.set('b', 2)
toArray(map) // [['a', 1], ['b', 2]]

// Iterator => Array
toArray(map.values()) // [1, 2]

// Object => Array
toArray({a: 1, b: 2}) // [['a', 1], ['b', 2]]

// Array-like object => Array
toArray({0: 'first', 1: 'second'}, {detectIndexKeys: true}) // ['first', 'second']

// Primitive value => Array
toArray('test') // ['test']

Converting to Iterators

const toIterator = require('2/iterator')

// Object => Iterator
let iterator = toIterator({a: 1, b: 2})
iterator.next().value // ['a', 1]
iterator.next().value // ['b', 2]
iterator.next().done // true

// Primitive value => Iterator
toIterator('test').next().value // 'test'

Converting to Maps

const toMap = require('2/map')

// Array of key/value pairs => Map
toMap([['a', 1], ['b', 2]])
map.get('a') // 1
map.get('b') // 2

// Array of values => Map
let map = toMap(['a', 'b'])
map.get(0) // 'a'
map.get(1) // 'b'

// Object => Map
map = toMap({a: 1, b: 2})
map.get('a') // 1
map.get('b') // 2

Converting to Numbers

const toNumber = require('2/number')

toNumber('1.2') // 1.2
toNumber(Infinity) // 0
toNumber(NaN) // 0
toNumber('not a number') // 0

// Can specify a fallback other than zero:
toNumber('not a number', {fallback: 100}) // 100

// You can choose to throw an error for invalid inputs by
// providing a null fallback:
toNumber('not a number', {fallback: null}) // throws error

// Option to round floats:
toNumber('4.7') // 4.7
toNumber('4.7', {round: true}) // 5

// By default, Infinity is not considered a valid number,
// but this can be changed:
toNumber(Infinity) // 0
toNumber(Infinity, {finite: false}) // Infinity

// Number object => Number
let numberObject = new Number(123)
typeof numberObject // 'object'
typeof toNumber(numberObject) // 'number'

Converting to Objects

const toObject = require('2/object')

// Array of key/value pairs => Object
let obj = toObject([['a', 1], ['b', 2]])
obj.a // 1
obj.b // 2

// Array => Object
let obj = toObject(['first', 'second'])
Object.keys(obj).length // 2
obj[0] // 'first'
obj[1] // 'second'

// In the above example, the array indices become the object keys.
// But you can make the keys mirror the values instead:
let obj = toObject(['first', 'second'], {mirror: true})
Object.keys(obj).length // 2
obj.first // 'first'
obj.second // 'second'

// Map => Object
let map = new Map()
map.set('key1', 'value1')
map.set('key2', 'value2')
let obj = toObject(map)
obj.key1 // 'value1'
obj.key2 // 'value2'

Converting to Strings

const toString = require('2/string')

toString(123) // '123'
toString(-0) // '0'

toString(true) // ''
toString(false) // ''
toString(undefined) // ''
toString(null) // ''
toString(Infinity) // ''
toString(NaN) // ''
toString({}) // ''
toString([]) // ''
toString(function () {}) // ''
toString(Symbol('test')) // ''

// Compare the above to standard JavaScript string conversion:
String(true) // 'true'
String(false) // 'false'
String(undefined) // 'undefined'
String(null) // 'null'
String(Infinity) // 'Infinity'
String(NaN) // 'NaN'
String({}) // '[object Object]'
String([]) // ''
String(function () {}) // 'function () {}'
String(Symbol('test')) // 'Symbol(test)'

// Default fallback is an empty string, but you can change it:
toString(undefined) // ''
toString(undefined, {fallback: 'N/A'}) // 'N/A'

// You can choose to throw an error for invalid inputs by
// providing a null fallback:
toString(undefined, {fallback: null}) // throws error

// String object => String
let stringObject = new String('test')
typeof stringObject // 'object'
typeof toString(stringObject) // 'string'