如何根据在 HTML5 中使用服务器发送事件检索到的数据显示通知

Question

I'm a beginner in HTML5. Now I'm trying to display the number of rows in a table using HTML5 Server-Sent Events. I was able to get the number of rows and display it inside a div tag.

Javascript

<script>
            var evtSource = new EventSource("messages.php");
            console.log("Inside 1");
            console.log(evtSource);
            evtSource.onmessage = function(e) {
            var no_of_messages=e.data;
            if(no_of_messages > 0)
                {
               $("#Messages").html(e.data);
                }
                else
                    {
               $("#Messages").html(e.data);
                }  

I used a PHP script to get the rows from the table.

PHP

<?php 
date_default_timezone_set("America/New_York");
header("Content-Type: text/event-stream\n\n");

$counter = rand(1, 10);
while (1) {
  // Every second, sent a "ping" event.

  echo "event: ping\n";
$dbhost = 'localhost:3036';
$dbuser = 'root';
$dbpass = 'password';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
  die('Could not connect: ' . mysql_error());
}
$sql = 'SELECT count(*) FROM messages';
mysql_select_db('apartment');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
  die('Could not get data: ' . mysql_error());
}
while($row = mysql_fetch_assoc($retval))
{
    $message_count=$row['count(*)'];
}
mysql_close($conn);

  echo 'data: {"Messages": "' . $message_count . '"}';
  echo "\n\n";

  // Send a simple message at random intervals.

  $counter--;

  if (!$counter) {
    echo 'data:' . $message_count . "\n\n";
    error_log($message_count);
    $counter = rand(1, 10);
  }

  ob_flush();
  flush();
  sleep(1);
}?>

Now, I want to display it as a notifications in the HTML page so that the user can see it as it pops up.

What I have done -

<div style="height: 70px; width:100%;border-style: solid;
        border-bottom-width:1px;border-color: #ccc" id="dashboard">    
        <div id="Messages"><button id="button" type="button">Number of Messages</button></div>        
        </div>      

With the above HTML I can display the Number of Messages, but I want to -
1. Change the color of the button when number of messages is above 0 and the color of the button should change to Green from initial color Red.
2. Is it possible to create a balloon like notification with this.

Answer 1

To change the color you can use

if (no_of_messages > 0){
    document.getElementById("button").style.background-color="red";
} else {
    document.getElementById("button").style.background-color="green";
}

But I am not too sure what is meant by 'balloon like', I will update my answer if you might explain a little bit more.