Source: carousel.js

/**
 * A Carousel  - <strike>UX/COE Compliant</strike>
 * <BR><BR><img src=../images/carousel.png width=80% style="border:1px lime dashed";>
 * <BR><BR><a href="../html/carousel.html">DEMO</a>
 */
class Carousel extends HTMLElement {
    constructor() {
        console.group("Carousel.constructor")
	
        super();
        console.groupEnd();
    };
    
    /**
     * Set observable values here. When Changed, attributeChangedCallback is invoked
     * @observedAttributes
     */
    static get observedAttributes() {
        console.group("Carousel.observedAttributes");
	this.observables = ["background"];
	console.log(this.observables);
        console.groupEnd();
        return this.observables;
    };
    /**
     * This function is called when this is attached to DOM
     * @connectedCallback. 
     */
    connectedCallback() {
        console.group("Carousel.connectedCallback")
	
	let self = this;
	// MAKE SURE OUR COMPONENT HAS GLOBAL CLASS
	this.classList.add("wc");
	// FETCH ALL INTERESTING ELEMENTS
	this._fetchElements();
	// FETCH ALL ATTRIBUTES
	this._fetchAttributes();
	let id = this.id;
	let tstr = "<div id='" + id + "-container" + "' class='carousel slide' data-ride='carousel'><ol class='carousel-indicators'>";
	
	for (let i=0; i<this.dom.items.length; i++) {
	    // ALWAYS ACTIVATE FIRST ITEM
	    let tmp = ""
	    if (i == 0) {
		tmp = " class='active'"
	    } else {
		tmp = ""
	    }
	    tstr += "<li data-target='#" + id + "-container" + "' data-slide-to='" + i + "'" + tmp + "></li>";
	}
	tstr += "</ol>";
	tstr += "<div class='carousel-inner'>";
	for (let i=0; i<this.dom.items.length; i++) {
	    // ALWAYS ACTIVATE FIRST ITEM
	    let tmp = ""
	    if (i == 0) {
		tmp = " active"
	    } else {
		tmp = ""
	    }
	    let caption = this.dom.items[i].getAttribute("caption");
	    tstr += "<div class='item" + tmp + "'>" +
		this.dom.items[i].querySelector("wc-carousel-item-content").innerHTML +
		"<div class='carousel-caption-fixed'>" + caption + "</div></div>";
	}
	tstr += "</div>";
	tstr += "<a class='left carousel-control' href='#" + id + "-container" + "' role='button' data-slide='prev'>"
	tstr += "<span class='glyphicon glyphicon-chevron-left'></span>"
	tstr += "<a class='right carousel-control' href='#" + id + "-container" + "' role='button' data-slide='next'>"
	tstr += "<span class='glyphicon glyphicon-chevron-right'></span>"
	this.innerHTML = tstr;
	// WRAP UP AND ADD STATS
	this._finalize();
	// SHOW IT NOW (NO FLICKERS) 
	this.style.visibility = "visible";
        console.groupEnd();
    };
    /**
     * Invoked When component is removed. Usually with a .remove() function call
     * @disconnectedCallback
     */
    disconnectedCallback() {
        console.group("Carousel.disconnectedCallback")
	/* CLEAN UP NOW */
        console.groupEnd();
    };
    /**
     * Called with .setAttribute(...) function call
     * @attributeChangedCallback
     */
    attributeChangedCallback(attr, oldval, newval) {
        console.group("Carousel.attributeChangedCallback:", attr, oldval, newval);
	this.properties = this.properties || [];
	// EXAMPLE ONLY. replace with observables
	switch(attr)
	{
	    case "background":
	    this.properties.background = newval;
	    this.style.background = this.properties.background;
	    break;
	}
	
        console.groupEnd();
    };
    /**
     * Stores DOM elements of interest for future use
     * @_fetchElements
     */
    _fetchElements() {
	console.group("Carousel._fetchElements");
	
	this.dom = this.dom || [];
	this.dom.content = this.innerHTML;
	this.dom.items = this.querySelectorAll("wc-carousel-item");
	console.groupEnd();
    };
    /**
     * Component attributes are _fetched and defaults are set if undefined
     * @_fetchAttributes
     * @param {string} [background=indianred] background color
     */
    _fetchAttributes() {
	console.group("Carousel._fetchAttributes");
	
	this.properties = {
	    "cname"      : "Carousel",
	    "author"     : "Mel Heravi",
	    "version"    : "1.0",
	    "background" : "indianred"
	};
	// EXAMPLE ONLY. replace with attributes
	if (this.hasAttribute("background")) {
	    this.properties.background = this.getAttribute("background");
	    console.log("background: ", this.properties.background);
	}
	console.groupEnd();
    };
    /**
     * Destroy the instance object and artifacts
     * @_destroy
     */
    destroy() {
	console.group("Message.destroy:", this.id);
	// FREE POINTER
	delete this;
	// REMOVE ITEM FROM DOM
	this.parentNode.removeChild(this);
	console.groupEnd();
    };
    /**
     * SAVE DATA FOR ANALYTICS
     * @__finalize
     */
    _finalize() {
	console.group("Carousel._finalize:", this.id);
	this.classList.add("wc");
	// ADD ANALYTICS HERE
	wc.getStats(this, this.properties.cname, this.properties.version);
	
	console.groupEnd();
    };
    /**
     * FOR TESTING PURPOSES
     * @test
     */
    static test() {
	console.group("Carousel.test");
	console.log("testing results will be printed here...");
	console.groupEnd();
	return true;
    }
}
window.customElements.define('wc-carousel', Carousel);