1.html

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>

2.js

// Send a message
PUBNUB.publish({ channel : 'chat', message : "hello!" })

3.js

// Receive messages
PUBNUB.subscribe({ channel : 'chat', message : fun })