“User is typing” function in chat

I'm trying to add in chat a "user is typing" function; chat written in PHP + MySQL/Ajax.

How it should work:

-when my chat partner X starts typing I see in my chat box: "X is typing"

-when I (named Y) am typing he sees in his chat box: "Y is typing" (just like Yahoo Messenger).

The code I've tried so far:

<script type="text/javascript" language="javascript">
    var timer = 0;

    function reduceTimer() {
        timer = timer - 1;
        isTyping(true);
    }

    function isTyping(val) {
        if (val == 'true') {
            document.getElementById('typing_on').innerHTML = "User is typing...";
        } else {

            if (timer <= 0) {
                document.getElementById('typing_on').innerHTML = "No one is typing -blank space.";
            } else {
                setTimeout("reduceTimer();", 500);
            }
        }
    }
</script>

<label>
    <textarea onkeypress="isTyping('true'); timer=5;" onkeyup="isTyping('false')" name="textarea" id="textarea" cols="45" rows="5"></textarea>
</label>
<div id="typing_on">No one is typing -blank speace.</div>

Questions:

If I stop for a few seconds to think about my spelling it looks like I've stopped typing. Is there a more relevant and less complicated way to set this function? Is there possible a code for:
- text box not empty (user pressed any key so started typing) -> Message: User is typing.
- text box empty -> Message: User is not typing.
- text box not empty, but user hasn't pressed any key for longer than 5 seconds -> Message: User is not typing.
It shows to myself that I am typing; how could I implement it or where, in order to see in my chat box the "X user is typing" and not "Myself is typing". Same for the other user, he should get a message about me typing/not typing , not about himself.

Thank you.

I have created a fiddle that might be helpful to you. The idea is to refresh activity message using javascript setInterval function.

var textarea = $('#textarea');
var typingStatus = $('#typing_on');
var lastTypedTime = new Date(0); // it's 01/01/1970, actually some time in the past
var typingDelayMillis = 5000; // how long user can "think about his spelling" before we show "No one is typing -blank space." message

function refreshTypingStatus() {
    if (!textarea.is(':focus') || textarea.val() == '' || new Date().getTime() - lastTypedTime.getTime() > typingDelayMillis) {
        typingStatus.html('No one is typing -blank space.');
    } else {
        typingStatus.html('User is typing...');
    }
}
function updateLastTypedTime() {
    lastTypedTime = new Date();
}

setInterval(refreshTypingStatus, 100);
textarea.keypress(updateLastTypedTime);
textarea.blur(refreshTypingStatus);

     <script>
        function isTyping() {
                document.getElementById('typing_on').innerHTML = "User is typing...! "; }

        function  notTyping (){
       document.getElementById('typing_on').innerHTML = "No one is typing ! "; }
    </script>

    <label>
        <textarea onkeypress="setTimeout(isTyping(),4000); setInterval(notTyping,5000)"  name="textarea" id="textarea" cols="45" rows="5"></textarea>
    </label>
    <div id="typing_on">No one is typing -blank speace.</div> 





    <!DOCTYPE html>
    <html>
       <head>
       </head>
       <body>

      <script>
        function isTyping() {
                document.getElementById('typing_on').innerHTML = "User is typing...! "; }
            
        function  notTyping (){
       document.getElementById('typing_on').innerHTML = "No one is typing ! "; }
    </script>

    <label>
        <textarea onkeypress="setTimeout(isTyping(),4000); setInterval(notTyping,5000)"  name="textarea" id="textarea" cols="45" rows="5"></textarea>
    </label>
    <div id="typing_on">No one is typing -blank speace.</div> 
       </body>
    </html>
来源：https://stackoverflow.com/questions/8963810/user-is-typing-function-in-chat

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ajax

chat