Enter Chat and press enter
<div><input id=input placeholder=you-chat-here /></div>

Chat Output
<div id=box></div>

<script src=http://cdn.pubnub.com/pubnub.min.js></script>
<script>(function(){
    var box = PUBNUB.$('box'), input = PUBNUB.$('input'), channel = 'chat';
        PUBNUB.subscribe({
            channel : channel,
            callback : function(text) { box.innerHTML = (''+text).replace( /[<>]/g, '' ) + '<br>' + box.innerHTML }
        });
        PUBNUB.bind( 'keyup', input, function(e) {
            (e.keyCode || e.charCode) === 13 && PUBNUB.publish({
            channel : channel, message : input.value, x : (input.value='')
        })
    } )
})()</script>