JSFiddle - React, Tailwind, and code Playground

HTML

<!--Container-->
		<div id="container">

				<ul id="tabs"><li id="tabAdd">+</li></ul>
			
		</div>

		<!--Popup window-->
		<div id="popup">

      		 <span href="#" id="x__popup"></span>

      		 <form id="form">

				Tab name: <input type="text" name="input" value="" maxlength="8" placeholder="Up to 8 characters" id="inputName">
				
				<a href="#" id="form__ok">Ok</a>

				<a href="#" id="form__cancel">Cancel</a>

			</form>
      
		</div>

		<!--Popup background-->
		<div id="popup__bgr"></div>

CSS

html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, font, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend, figure,
table, caption, tbody, tfoot, thead, tr, th, td {
margin: 0;
padding: 0;
border: 0;
outline: 0;
background: transparent;
vertical-align: baseline;
}

ol, ul {
list-style: none;
}
blockquote, q {
quotes: none;
}
:focus {
outline: 0;
}
ins {
text-decoration: none;
}
del {
text-decoration: line-through;
}
table {
border-collapse: collapse;
border-spacing: 0;
}

html {
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
}

*, *:before, *:after {
-webkit-box-sizing: inherit;
-moz-box-sizing: inherit;
box-sizing: inherit;
}
/*Reset above*/

@import url(http://fonts.googleapis.com/css?family=Titillium+Web);

/*Main container*/
#container {
	background-color: #2c3e50;
	font-size: 0;
	margin: 150px auto;
	height: 400px;
}


/*Tabs*/
.item {
	background-color: #f1c40f;
	font-size: 14px;
	display: inline-block;
	text-align: center;
	width: 100px;
	height: 40px;
	position: relative;
	vertical-align: top;
	line-height: 46px;
	border-left: 1px solid red;
	text-transform: lowercase;
}

.item:hover {
	background-color: #d35400;
}

/*Add a tab*/
#tabAdd {
	color: #fff;
	width: 40px;
	height: 40px;
	position: relative;
	display: inline-block;
	font-size: 35px;
	background-color: #d35400;
	vertical-align: top;
	text-align: center;
	margin-right: 3px;
}

#tabAdd:hover {
	background-color: #e98b39;
	color: #2c3e50;
	cursor:pointer;
}


.close {
	position: absolute;
	top: 3px;
	left: 78px;
	height: 20px;
	width: 20px;
	line-height:20px;
	cursor: pointer;
	font-size: 12px;
	opacity: .6;
}



/*Popup window*/
#popup {
	width: 300px; 
	height: 200px;
	border-radius: 5px;
	border: 3px #000 solid;
	background: #fff;
	position: fixed; /* чтoбы oкнo былo в...

JavaScript

$( document ).ready( function() {


/********** Click New tab *******/
	$("#tabAdd").click( function(){

		$( "#popup__bgr" ).fadeIn( 300,

		function(){

			$( "#popup" ) 
			.css( "display", "block" )
			.animate({ opacity: 1, top: '50%' }, 200)

		});



		$( function(){

			$( "#inputName").val("");

		});

	});


/*********** Click Ok ************/
$( "#form__ok" ).click( function(){

			var $name = $( "#inputName" ).val();

			if( $name == "" ){

				alert( "Please, gimme a name" );
				return false;
			};

				

			var newTab = $( "<li class='item'></li>" );
			newTab.text( $name );

			
			newTab.insertBefore( "#tabAdd" ).hide().fadeIn( 600 );
			var $span = $( "<span class='close'>&#10006;</span>" );
			$span.appendTo( newTab );

			/*********Remove a tab******/
			$( ".close" ).click( function(){

				$( this ).closest( "li" ).fadeOut( 200, function() {$( this ).remove();});

			});



			$( "#popup__bgr" )
			.animate({ opacity: 0, top: '45%' }, 200,

				function(){

					$( "#popup" ).css( "display", "none" );
					$( "#popup__bgr" ).fadeOut( 200 );
					$( "#popup__bgr" ).removeAttr('style');//REMOVE STYLES OF THE POPUP BACKGROUND!

				}
			);

})



/********Click Cancel / Background or Close **********/
	$( "#x__popup, #popup__bgr, #form__cancel" ).click( function(){
		
		$( "#popup__bgr" )
			.animate({ opacity: 0, top: '45%' }, 200,
				function(){
					$( "#popup" ).css( "display", "none" );
					$( "#popup__bgr" ).fadeOut( 200 ).removeAttr('style');//REMOVE STYLES OF THE POPUP BACKGROUND!
				}
			);

	});

});