I am new to js and I am trying tutorials for a countdown clock with buttons to activate the functions. I have gotten it to start and countdown to 0 then alert a message and I got a clear button that clears it to 0 and a stop button to stop at whatever time before 0. My problem is I have not been able to get a button to work to resume the countdown at the time stopped. Was wondering if anyone can help out? Here is the code I have for the 3 buttons. How can I do a function for the time it is stopped at?

________________js code____________________

var running = false
var endTime = null
var timerID = null
function startTimer() {
running = true
now = new Date()
now = now.getTime()
// change last multiple for the number of minutes
endTime = now + (1000 * 30 * 1)
showCountDown()
}
function showCountDown() {
var now = new Date()
now = now.getTime()
if (endTime - now <= 0) {
stopTimer()

alert("Time is up. Get back to work!.")
} else {
var delta = new Date(endTime - now)
var theMin = delta.getMinutes()
var theSec = delta.getSeconds()
var theTime = theMin
theTime += ((theSec < 10) ? ":0" : ":") + theSec
document.forms[0].timerDisplay.value = theTime
if (running) {
timerID = setTimeout("showCountDown()",1000)
}
}
}
function stopTimer() {
clearTimeout(timerID)
running = false
document.forms[0].timerDisplay.value = "0:00"
}

function stopTimertwo() {
clearTimeout(timerID)
running = false
document.forms[0].timerDisplay.value = theTime
}

_____________HTML code___________________

<html>
<head>
<title>Countdown clock</title>

<script type = "text/javascript" src="clock.js"></script>

</head>

<body>

<FORM>
<INPUT TYPE="button" NAME="startTime" VALUE="Start/Reset"
onClick="startTimer()">
<INPUT TYPE="button" NAME="stopTime" VALUE="Stop Timer"
onClick="stopTimertwo()">
<INPUT TYPE="button" NAME="clearTime" VALUE="Clear Timer"
onClick="stopTimer()">
<INPUT TYPE="text" NAME="timerDisplay" VALUE="0:30">
</FORM>

</body>
</html>