@egjs/visible/src/utils.js

A class that checks if an element is visible in the base element or viewport.

const SUPPORT_ADDEVENTLISTENER = !!("addEventListener" in document);
const SUPPORT_PASSIVE = (() => {
	let supportsPassiveOption = false;

	try {
		if (SUPPORT_ADDEVENTLISTENER && Object.defineProperty) {
			document.addEventListener("test", null, Object.defineProperty({},
				"passive", {
					get() {
						supportsPassiveOption = true;
					},
				}));
		}
	} catch (e) { }
	return supportsPassiveOption;
})();

export function toArray(nodes) {
	// SCRIPT5014 in IE8
	const array = [];

	if (nodes) {
		for (let i = 0, len = nodes.length; i < len; i++) {
			array.push(nodes[i]);
		}
	}
	return array;
}

/**
 * Select or create element
 * @param {String|HTMLElement|jQuery} param
 *  when string given is as HTML tag, then create element
 *  otherwise it returns selected elements
 * @param {Boolean} multi
 * @returns {HTMLElement|HTMLElement[]|undefined}
 */
export function $(param, multi = false) {
	let el;

	if (param === undefined) {
		return undefined;
	}

	if (typeof param === "string") { // String (HTML, Selector)
		// check if string is HTML tag format
		const match = param.match(/^<([a-z]+)\s*([^>]*)>/);

		// creating element
		if (match) { // HTML
			const dummy = document.createElement("div");

			dummy.innerHTML = param;
			el = toArray(dummy.childNodes);
		} else { // Selector
			el = toArray(document.querySelectorAll(param));
		}
		if (!multi) {
			el = el.length >= 1 ? el[0] : undefined;
		}
	} else if (param === window) { // window
		el = param;
	} else if (param.nodeName &&
		(param.nodeType === 1 || param.nodeType === 9)) { // HTMLElement, Document
		el = param;
	} else if (("jQuery" in window && param instanceof jQuery) ||
		param.constructor.prototype.jquery) { // jQuery
		el = multi ? param.toArray() : param.get(0);
	} else if (Array.isArray(param)) {
		el = param.map(v => $(v));
		if (!multi) {
			el = el.length >= 1 ? el[0] : undefined;
		}
	}
	return el;
}
export function getWindowRect() {
	// [IE7] document.documentElement.clientHeight has always value 0 (bug)
	return {
		top: 0,
		left: 0,
		bottom: window.innerHeight ||
			document.documentElement.clientHeight ||
			document.body.clientHeight,
		right: window.innerWidth ||
			document.documentElement.clientWidth ||
			document.body.clientWidth,
	};
}
export function hasClass(el, className) {
	if (el.classList) {
		return el.classList.contains(className);
	} else {
		return new RegExp(`(^| )${className}( |$)`, "gi").test(el.className);
	}
}
export function addEvent(element, type, handler, eventListenerOptions) {
	if (SUPPORT_ADDEVENTLISTENER) {
		let options = eventListenerOptions || false;

		if (typeof eventListenerOptions === "object") {
			options = SUPPORT_PASSIVE ? eventListenerOptions : false;
		}
		element.addEventListener(type, handler, options);
	} else if (element.attachEvent) {
		element.attachEvent(`on${type}`, handler);
	} else {
		element[`on${type}`] = handler;
	}
}
export function removeEvent(element, type, handler) {
	if (element.removeEventListener) {
		element.removeEventListener(type, handler, false);
	} else if (element.detachEvent) {
		element.detachEvent(`on${type}`, handler);
	} else {
		element[`on${type}`] = null;
	}
}