检测聊天窗口中的用户响应

i am making an interviewing chatbot using programO (i am new to php) in which i want to display a message if for long time there is no activity on chat window. i hav searched jquery plugins but they are for detecting mouse or keyboard strokes but i am just concerend with detecting that whether the chat window is upadted with a user input or not . i hav also searched javascript settimeout and settimeinterval functions to display a message but i am unable to understand how to use them with chat window form.

setTimeout needs to be used in conjunction with clearTimeout. Use clearTimeout whenever a time resetting event occurs.

Example:

<script>
    var interval = -1;
    var TIMEOUT = 5; // seconds
    function doTimeout(){
        alert('show timeout message');
        startClock(); // if you want to restart the timer
    }
    function startClock(event){
        console.log("foo",interval, event);
        if(interval !== -1){
            console.log("clearing timeout");
            clearTimeout(interval);
        }
        interval = setTimeout(doTimeout,TIMEOUT*1000);
    }
    startClock(); // if you want to start the timer on arrival
</script>

<!-- add remove events as you see fit -->
<textarea id="chatinput" onblur="startClock(event)" onfocus="startClock(event)" onchange="startClock(event)" onkeyup="startClock(event)"></textarea>

For more on timeout:
tags: settimeoutsetinterval
questions: javascript setTimeout clearTimeout