Source: nav.js

/**
 * A NAVIGATION COMPONENT <BR>
 * <BR><BR><img src=../images/nav.png width=50% style="border:1px lime dashed";>
 * <BR><BR><a href="../html/nav.html">DEMO</a>
 */
class Nav extends HTMLElement {
    constructor() {
        console.group("Nav.constructor")
	
        super();

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

	this.observables = ["config", "direction"];
	console.log(this.observables);

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

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

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

	// FETCH ALL ATTRIBUTES
	this._fetchAttributes();

	if (this.properties.config) {
	    // IF WE HAVE A CONFIG PROPERTY
	    let url = location.protocol + "//" + location.host + this.properties.config;
	    
	    $.getJSON(url, function(data) {
		let str = "<ul class='list-group'>";
		
		for (var i = 0; i < data.length; i++) {
		    str += "<a href='" + data[i].url + "' id='" + data[i].id + "' class='list-group-item " + self.properties.direction + "'>" + data[i].text + "</a>";
		}
		
		str += "</ul>";
		
		self.innerHTML = str;

		let links = self.querySelectorAll(".list-group-item");
		
		for (i=0; i < links.length; i++) {
		    let link = links[i];

		    links[i].addEventListener("click", function() {
			self._onClick(link);
		    });
		}
	    });
	} else {
	    // IF WE HAVE A INLINE LINKS
	    let links = this.querySelectorAll("wc-nav-links a");
	    let str = "<ul class='list-group'>";
	    
	    for (let i = 0; i < links.length; i++) {
		let link = links[i];

		link.classList.add(self.properties.direction);
		link.classList.add("list-group-item");
		
		str += link.outerHTML;

		link.addEventListener("click", function() {
		    self._onClick(link);
		});
	    }
	    str += "</ul>";
	}

	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("Nav.disconnectedCallback")

	/* CLEAN UP NOW */

        console.groupEnd();
    };

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

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

	switch(attr)
	{
	    case "config":
	    this.properties.config = newval;
	    break;

	    case "direction":
	    this.properties.direction = newval;
	    break;
	}
	
        console.groupEnd();
    };

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

	console.groupEnd();
    };

    /**
     * Component attributes are _fetched and defaults are set if undefined
     * @_fetchAttributes
     * @param {string} config JSON config file
     * @param {string} [direction=vertical] direction of items
     */
    _fetchAttributes() {
	console.group("Nav._fetchAttributes");
	
	this.properties = {
	    "cname"	 : "Nav",
	    "author"     : "Mel Heravi",
	    "version"    : "1.0",
	    "config"	 : null,
	    "direction"	 : "vertical",
	};
	
	if (this.hasAttribute("config")) {
	    this.properties.config = this.getAttribute("config");
	    console.log("config: ", this.properties.config);
	}

	if (this.hasAttribute("direction")) {
	    this.properties.direction = this.getAttribute("direction");
	    console.log("direction: ", this.properties.direction);
	}

	console.groupEnd();
    };

    /**
     * A sample callback usage function - see connectedCallback()
     * @_onClick
     */
    _onClick(link) {
	console.group("Nav._onClick:", link);

	// REMOVE ALL ACTIVES
	$("#" + this.id + " .list-group-item").removeClass("active");

	// MAKE CLICKED LINK ACTIVE
	link.classList.add("active");

	wc.publish(this, "wc-nav", {
	    action: "click",
	    nav: this.id,
	    id: link.id
	});

	console.groupEnd();
    };

    /**
     * Destroy the instance object and artifacts
     * @_destroy
     */
    destroy() {
	console.group("Nav.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("Nav._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("Nav.test");

	console.log("testing results will be printed here...");

	console.groupEnd();
	return true;
    };
    
    /**
     * FETCH JSON FILE
     * @_getJSON
     */
    _getJSON(path,callback) {
	console.group("nav._getJSON");
	
	var url = location.protocol + "//" + location.host + "/" + path;
	
	var xhr = new XMLHttpRequest();
	xhr.open("get", url, true);
	xhr.responseType = "json";
	xhr.onload = function() {
	    var status = xhr.status;
	    if (status == 200) {
		callback(null, xhr.response);
	    } else {
		callback(status);
	    }
	};

	xhr.send();
	console.groupEnd();
	return true;
    };
}

window.customElements.define('wc-nav', Nav);