simpleTimer.js

function buildTime(t) {
    minutes = t.getMinutes();
    seconds = t.getSeconds();
    hours = t.getHours();
    if (minutes < 10) {
        minutes = "0"+minutes;
    }
    if (seconds < 10) {
        seconds = "0"+seconds;
    }
    if (hours > 0) {
        return hours+":"+minutes+":"+seconds;
    } else {
        return minutes+":"+seconds;
    }
}

// Call this to start the timer
function startTimer() {
    // If time isn't an object, create new Date and set seconds/minutes to 0
    if (typeof(time) != "object") {
        time = new Date();
        time.setSeconds(0); // Sets seconds to 0
        time.setMinutes(0); // Sets minutes to 0
        document.getElementById("show_timer_div").innerHTML = buildTime(time); // buildTime(time) returns 00:00
    }
    // Update seconds, to be executed every second or 1000 miliseconds
    function changeTimer() {
        time.setSeconds(time.getSeconds()+1);
        document.getElementById("show_timer_div").innerHTML = buildTime(time);
    }
    // Set Interval to every second
    interval = setInterval(changeTimer, 1000);
}

// Pauses timer, seconds/minute count will be the same when started again
function pauseTimer() {
    clearInterval(interval);
}

// Reset timer to 00:00
function resetTimer() {
    time = ""; // Turn time into a string
    clearInterval(interval); // Clear interval
    document.getElementById("show_timer_div").innerHTML = "00:00"; // Put timer to 0's
}