var tab = {
	nav: null, // holds all tabs.
	txt: null, // holds all text containers.
	init: function () {
		// Get all tabs + contents.
		var em_tab_nav = document.getElementById( 'em-tab-nav' );
		if ( null === em_tab_nav ) {
			return;
		}
		tab.nav = em_tab_nav.getElementsByClassName( 'em-tabnav' );
		tab.txt = document.getElementById( 'em-tab-contents' ).getElementsByClassName( 'em-tabtxt' );

		// Error checking.
		if ( 0 === tab.nav.length || 0 === tab.txt.length || tab.nav.length !== tab.txt.length ) {
			console.log( 'ERROR STARTING TABS' );
		} else {
			// Attach onclick events to navigation tabs.
			var nav_items = tab.nav.length;
			for ( var i = 0; i < nav_items; i ++ ) {
				tab.nav[i].dataset.pos = i;
				tab.nav[i].addEventListener( 'click', tab.switch );
			}

			// Default - show first tab.
			tab.nav[0].classList.add( 'active' );
			tab.txt[0].classList.add( 'active' );
		}
	},

	switch : function() {
		// Hide all tabs & text.
		var nav_length = tab.nav.length;
		for (var i = 0; i < nav_length; i++) {
			tab.nav[i].classList.remove( 'active' );
			tab.nav[i].classList.toggle( 'tab-navs-open' );
		}
		var txt_length = tab.txt.length;
		for (var x = 0; x < txt_length; x++) {
			tab.txt[x].classList.remove( 'active' );
			tab.txt[x].classList.toggle( 'tab-text-hide' );
		}
		// Set current tab.
		tab.nav[this.dataset.pos].classList.add( 'active' );
		tab.txt[this.dataset.pos].classList.add( 'active' );
	}
};

window.addEventListener( 'load', tab.init );