A very very very crude and malformed and plain dumb version of jquery

crude-jquery.js

/**
 * Created by Braynstorm on 9.4.2016 г..
 */
'use strict';
var debugMode = false;

function $ (str) {
	if (str instanceof HTMLElement)
		return modifySelectedObject(str);

	return modifySelectedObject(document.querySelectorAll(str));
}

function modifySelectedObject (list) {
	if(list instanceof HTMLElement || list instanceof HTMLDocument || list instanceof SVGElement) {
		list.toggleClass = function (className) {
			this.classList.toggle(className);
			return this;
		};

		list.addClass = function (className) {
			this.classList.add(className);
			return this;
		};

		list.hasClass = function (className) {
			return this.classList.contains(className);
		};

		list.removeClass = function (className) {
			this.classList.remove(className);
			return this;
		};

		list.attr = function (name, val){
			if(typeof val === 'undefined'){
				return list.getAttribute(name);
			}

			list.setAttribute(name, val);

			return list;
		};

		list.html = function (val){
			if(typeof val === 'undefined'){
				return list.innerHTML;
			}

			list.innerHTML = val;

			return list;
		};

		list.css = function (rules, val) {
			for (var i in rules) {
				list.style[i] = rules[i];
			}
			return this;
		};

		// Performance, yo!
		list.getStyle = function () {
			return window.getComputedStyle(this, null);
		};

		list.cacheCurrentStyle = function () {
			this.cachedStyle = this.getStyle();
			return this;
		};

		list.getCachedStyle = function () {
			return this.cachedStyle;
		};

		//Events
		list.onMouseDown = function (callback) {
			list.addEventListener("mousedown", callback);
			return this;
		};

		list.onMouseUp = function (callback) {
			list.addEventListener("mouseup", callback);
			return this;
		};

		list.onMouseOver = function (callback) {
			list.addEventListener("mouseover", callback);
			return this;
		};

		list.onMouseOut = function (callback) {
			list.addEventListener("mouseout", callback);
			return this;
		};

		list.onMouseMove = function (callback) {
			list.addEventListener("mousemove", callback);
			return this;
		};

		list.onContextMenu = function (callback) {
			list.addEventListener("contextmenu", callback);
			return this;
		};

		list.onMouseWheel = function (callback) {
			list.addEventListener("wheel", callback);
			return this;
		};


		return list;
	} else if (list.length == 1){
		return modifySelectedObject(list[0]);
	} else {
		var newList = [];

		for (var i in list) {
			if(list[i] instanceof HTMLElement|| list[i] instanceof HTMLDocument || list[i] instanceof SVGElement)
				newList.push(modifySelectedObject(list[i]));
		}

		return newList;
	}
}

function $$ (str) {
	return document.querySelectorAll(str);
}

function $ready(func){
	document.addEventListener("ready", func);
}

function debug (f) {
	if(debugMode === true)
		console.log(f);
}

function $create (tagName, attributes) {
	var element = document.createElement(tagName);

	for (var i in attributes)
		element.attr(i, attributes[i]);

	return modifySelectedObject([element]);
}

function $createDiv (attributes) {
	return $create("div", attributes);
}

class Animation {
	constructor (element, property, endValue, time, callback) {
		if (typeof BoxObject !== "undefined" && element instanceof BoxObject)
			this.element = element.obj;
		else
			this.element = element;

		this.property   = property;
		this.totalTime  = time;
		this.passedTime = 0;
		this.suffix     = "";
		this.callback   = callback;
		this.isRunning  = false;

		this.startValue = this.element.getStyle()[property];

		if (typeof this.startValue === "string") {
			this.startValue = Utils.stripPx(this.startValue);
			this.suffix     = "px";
		}


		if (typeof endValue === "string") {
			this.endValue = Utils.stripPx(endValue);
			this.suffix   = "px";
		} else
			this.endValue = endValue;

		this.currentValue = this.startValue;

		this.operationsPerMs = (this.endValue - this.startValue) / this.totalTime;
	}

	go () {
		if (!this.isRunning)
			if (this.alreadyWent)
				this.goBackwards();
			else
				this.goForwards();

	}

	goForwards () {
		if (this.passedTime < this.totalTime) {// a.k.a Epsilon
			this.alreadyWent = true;
			this.isRunning   = true;
			setTimeout(() => {
				this.passedTime += 10;
				this.currentValue += this.operationsPerMs * 10;
				this.element.style[this.property] = Math.round(this.currentValue) + this.suffix;

				this.goForwards();
			}, 10);
		} else {
			this.isRunning = false;
			if (this.callback !== undefined && typeof this.callback === "function")
				this.callback();
		}
	}

	goBackwards () {
		var swap             = this.startValue;
		this.startValue      = this.endValue;
		this.endValue        = swap;
		this.passedTime      = 0;
		this.currentValue    = this.startValue;
		this.operationsPerMs = -this.operationsPerMs;
		this.alreadyWent     = false;

		this.goForwards();
	}
}

class Utils {
	/**
	 * 25px => 25.
	 * @param str
	 * @returns {Number}
	 */
	static stripPx (str) {
		return parseInt(str.substring(0, str.indexOf("p")));
	}

	static sqr (n) {
		return n * n;
	}

	/**@param {Number} val
	 * @param {Number} min
	 * @param {Number} max
	 * @return {Number} */
	static clamp (val, min, max) {
		return val > max ? max : (val < min ? min : val);
	}

	static arrayFromIterator(it){
		var next;
		var arr = [];

		while(true){
			next = it.next();

			if(next.done === true)
				break;

			arr.push(next.value);
		}

		return arr;
	}

}