app.js

const cosa = (function() {
	'use strict'

	// Holds our public methods
	const methods = {}

	/**
	 * Array.from() polyfill
	 */
	// From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from
	// Production steps of ECMA-262, Edition 6, 22.1.2.1
	if (!Array.from) {
		Array.from = (function() {
			var toStr = Object.prototype.toString
			var isCallable = function(fn) {
				return (
					typeof fn === 'function' || toStr.call(fn) === '[object Function]'
				)
			}
			var toInteger = function(value) {
				var number = Number(value)
				if (isNaN(number)) {
					return 0
				}
				if (number === 0 || !isFinite(number)) {
					return number
				}
				return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number))
			}
			var maxSafeInteger = Math.pow(2, 53) - 1
			var toLength = function(value) {
				var len = toInteger(value)
				return Math.min(Math.max(len, 0), maxSafeInteger)
			}

			// The length property of the from method is 1.
			return function from(arrayLike /*, mapFn, thisArg */) {
				// 1. Let C be the this value.
				var C = this

				// 2. Let items be ToObject(arrayLike).
				var items = Object(arrayLike)

				// 3. ReturnIfAbrupt(items).
				if (arrayLike == null) {
					throw new TypeError(
						'Array.from requires an array-like object - not null or undefined'
					)
				}

				// 4. If mapfn is undefined, then let mapping be false.
				var mapFn = arguments.length > 1 ? arguments[1] : void undefined
				var T
				if (typeof mapFn !== 'undefined') {
					// 5. else
					// 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
					if (!isCallable(mapFn)) {
						throw new TypeError(
							'Array.from: when provided, the second argument must be a function'
						)
					}

					// 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
					if (arguments.length > 2) {
						T = arguments[2]
					}
				}

				// 10. Let lenValue be Get(items, "length").
				// 11. Let len be ToLength(lenValue).
				var len = toLength(items.length)

				// 13. If IsConstructor(C) is true, then
				// 13. a. Let A be the result of calling the [[Construct]] internal method
				// of C with an argument list containing the single item len.
				// 14. a. Else, Let A be ArrayCreate(len).
				var A = isCallable(C) ? Object(new C(len)) : new Array(len)

				// 16. Let k be 0.
				var k = 0
				// 17. Repeat, while k < len… (also steps a - h)
				var kValue
				while (k < len) {
					kValue = items[k]
					if (mapFn) {
						A[k] =
							typeof T === 'undefined'
								? mapFn(kValue, k)
								: mapFn.call(T, kValue, k)
					} else {
						A[k] = kValue
					}
					k += 1
				}
				// 18. Let putStatus be Put(A, "length", len, true).
				A.length = len
				// 20. Return A.
				return A
			}
		})()
	}

	//
	// Methods
	//

	/**
	 * Convert an array-like object into an array
	 * @param  {*}     list An array-like object (ex. NodeList)
	 * @return {Array}      An array
	 */
	methods.toArray = list => Array.from(list)

	/**
	 * Get the first element that match a selector
	 * @param  {String} selector The selector
	 * @return {Node}            The matching element
	 */
	methods.get = selector => document.querySelector(selector)

	/**
	 * Get all elements that match a selector
	 * @param  {String} selector The selector
	 * @return {Array}           The matching elements
	 */
	methods.getAll = selector =>
		methods.toArray(document.querySelectorAll(selector))

	/**
	 * Add a class to all elements in an array
	 * @param  {Array}  elems     The elements
	 * @param  {String} className The class to add
	 */
	methods.addClass = (elems, className) =>
		elems.forEach(elem => elem.classList.add(className))

	/**
	 * Remove a class to all elements in an array
	 * @param  {Array}  elems     The elements
	 * @param  {String} className The class to remove
	 */
	methods.removeClass = (elems, className) =>
		elems.forEach(elem => elem.classList.remove(className))

	//
	// Return the public methods
	//
	return methods
})()

/**
 * TESTING
 */

// cosa.toArray()
const arr = cosa.toArray(document.querySelectorAll('button'))
console.log('cosa.toArray()', arr)

// cosa.get()
var btn = cosa.get('#button-2')
console.log('cosa.get()', btn)

// cosa.getAll()
var btns = cosa.getAll('button')
console.log('cosa.getAll()', btns)

// cosa.addClass()
cosa.addClass(btns, 'btn-purple')

// cosa.removeClass()
cosa.removeClass(btns, 'btn-blue')