JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://modernizr.com/downloads/modernizr-2.5.3.js"></script>
<p>BEGIN</p>

JavaScript

function checkMq() {
    if (Modernizr.mq('(min-width: 600px)')) {
        $('<div>')
        .attr('id','small')
        .html('siamo ---oltre---- i 600px')
        .appendTo('body')
    } else {
        $('<div>')
            .attr('id','wide')
            .html('siamo ---sotto--- i 600px')
            .appendTo('body')
    }
}

$(function() {
    // the call to checkMq here will execute after the document has loaded
    //checkMq();

    $(window).resize(function() {
        // the call to checkMq here will execute every time the window is resized
        checkMq();
    });

    // you can add other listeners here click, hover, etc.  
});

checkMq();