Source: card.js

/**
 * Card Component<BR>
 * <BR><BR><img src=/tk/lib/components/w/img/card.png width=80% style="border:1px lime dashed;padding:20px">
 * <BR><BR><a href="/tk/lib/components/w/html/card.html">DEMO</a>
 */
class Card extends HTMLElement {
    constructor() {
        wc.group("Card.constructor")
	
        super();

        wc.groupEnd();
    };
    
    /**
     * Set observable values here. When Changed, attributeChangedCallback is invoked
     * @observedAttributes
     */
    static get observedAttributes() {
        wc.group("Card.observedAttributes");

	this.observables = [];

        wc.groupEnd();
        return this.observables;
    };

    /**
     * This function is called when this is attached to DOM
     * @connectedCallback. 
     */
    connectedCallback() {
        wc.group("Card.connectedCallback")
	
	let self = this;

	// GET PROPERTIES AND INTERESTING ELEMENTS
	this._initialize();

	if (this.properties.cfg) {
	    this.configure();
	}

	// ADD STATS AND OTHER FINAL STUFF
	this._finalize();

        wc.groupEnd();
    };

    /**
     * Invoked When component is removed. Usually with a .remove() function call
     * @disconnectedCallback
     */
    disconnectedCallback() {
        wc.group("Card.disconnectedCallback")

	/* CLEAN UP NOW */

        wc.groupEnd();
    };

    /**
     * Called with .setAttribute(...) function call
     * @attributeChangedCallback
     */
    attributeChangedCallback(attr, oldval, newval) {
        wc.group("Card.attributeChangedCallback:", attr, oldval, newval);

	this.properties = this.properties || [];

	let obs = Card.observedAttributes;

	for (let i = 0; i < obs.length; i++) {
	    if (newval) {
		this.properties[obs[i]] = newval;
	    }
	}
	
	// YOUR CODE FOR CHANGES GO HERE (MAYBE NULL FIRST TIME THROUGH)
	try {
	    switch(attr) 
	    {
		case "background":
		break;
		
		default:
		break;
	    }
	}
	catch(e) {
	    wc.warn(e.name + ' > ' + e.message);
	}

        wc.groupEnd();
    };

    /**
     * Stores DOM elements of interest for future use
     * @private
     * @_fetchElements
     */
    _fetchElements() {
	wc.group("Card._fetchElements");
	
	this.dom = this.dom || [];
	this.dom.content = this.innerHTML;

	wc.groupEnd();
    };

    /**
     * Component attributes are _fetched and defaults are set if undefined
     * @private
     * @_fetchAttributes
     * @param {string} [modal=true] mode for our card
     */
    _fetchAttributes() {
	wc.group("Card._fetchAttributes");
	
	this.properties = {
	    cname      : "Card",
	    author     : "Mel Heravi",
	    version    : "1.0",
	};
	
	// SAVE WIDGET SPECIFIC PROPERTIES
	this.propertiesW = [];

	// SAVE ALL OTHER PROPERTIES
	let attrs = wc.getAttributes(this)
	
 	for (var key in attrs) {
	    let attr = this.getAttribute(key) || this.properties.key;
	    this.properties[key]  = this.getAttribute(key);
	    this.propertiesW[key] = this.getAttribute(key);
	    wc.log(key + ": " + attrs[key]);
	}

	// SET ALL INITIAL ATTRIBUTES
 	for (var key in this.properties) {
	    switch(key) 
	    {
		case "header":
		let h = document.querySelector("wc-header")
		//h.innerHTML = this.properties.header;
		break;
		
		default:
		break;
	    }
	}

	wc.log("ATTRIBUTES: ", this.properties);

	wc.groupEnd();
    };

    /**
     * A sample callback usage function - see connectedCallback()
     * @private
     * @_onClick
     */
    _onClick() {
	wc.group("Card._onClick:", this.id);

	wc.publish("wc-card", {
	    action: "click",
	    id: this.id,
	    uparam: this.properties.uparam
	});

	wc.groupEnd();
    };

    /**
     * Destroy the instance object and artifacts
     * @private
     * @_destroy
     */
    destroy() {
	wc.group("Card.destroy:", this.id);

	// FREE ALL MEMORY
	// you should delete all created objects here

	// FREE POINTER
	delete this;

	// REMOVE ITEM FROM DOM
	this.parentNode.removeChild(this);

	wc.groupEnd();
    };

    /**
     * configure the instance object and artifacts
     * @configure
     */
    configure(aname) {
	wc.group("Card.configure:", aname);

	// IF JSON VARIABLE (aname) IS PROVIDED
	if (aname) {
	    this.process(aname);
	} else {
	    let self = this;

	    $.getJSON(this.properties.cfg, function(data) {
		self.process(data);
	    }).fail(function(jqXHR, textStatus, errorThrown) {
		alert("incoming Text " + jqXHR.responseText);
	    });
	}
	
	wc.groupEnd();
    };

    /**
     * configure the instance object and artifacts
     * @configure
     */
    process(data) {
	wc.group("Card.process:", data);

	this.innerHTML = `
		<div class="card">
		    <span class="img-top"></span>

		    <div class="card-body">
			This is some text within a card block.
		    </div>

		    <span class="img-bottom"></span>
		</div>`

	var tmp;
	var card = this.querySelector(".card");

	if (typeof data.header != "undefined") {
	    $(card).prepend("<div class='card-header'>HEADER</div>");
	    tmp = this.querySelector(".card-header");
	    tmp.innerHTML = data.header.value;
	} else {
	    $(this.querySelector(".card-header")).remove();
	}
	
	if (typeof data.footer != "undefined") {
	    $(card).append("<div class='card-footer'>FOOTER</div>");
	    tmp = this.querySelector(".card-footer");
	    tmp.innerHTML = data.footer.value;
	} else {
	    $(this.querySelector(".card-footer")).remove();
	}
	
	tmp = this.querySelector(".card-body");
	tmp.innerHTML = data.body.value;
	
	switch(data.imageposition.value) 
	{
	    case "Top":
	    tmp = this.querySelector(".img-top");
	    $(tmp).html(`<img class="card-img-top" src="${data.image.value}" alt="Card image cap">`);
	    break;

	    case "Bottom":
	    tmp = this.querySelector(".img-bottom");
	    $(tmp).html(`<img class="card-img-bottom" src="${data.image.value}" alt="Card image cap">`);
	    break;

	    case "Cover":
	    tmp = this.querySelector(".card-body");
	    $(tmp).css({
		"background":"url(" + data.image.value + ")",
		"background-size":"cover",
		"background-repeat": "no-repeat",
		"background-position": "center"
	    });
	    break;

	    default:
	    break;
	}

	wc.groupEnd();
    };

    /**
     * SAVE DATA FOR ANALYTICS
     * @private
     * @_initialize
     */
    _initialize() {
	wc.group("Card._initialize:", this.id);

	// FETCH ALL INTERESTING ELEMENTS
	this._fetchElements();

	// FETCH ALL ATTRIBUTES
	this._fetchAttributes();
	
	wc.groupEnd();
    };

    /**
     * SAVE DATA FOR ANALYTICS
     * @private
     * @_finalize
     */
    _finalize() {
	wc.group("Card._finalize:", this.id);

	this.classList.add("wc");

	// ADD ANALYTICS HERE
	wc.setStats(this, this.properties.cname, this.properties.version);
	
	// SHOW IT NOW (NO FLICKERS) 
	this.style.visibility = "visible";

	wc.groupEnd();
    };
}

window.customElements.define('wc-card', Card);