javascript - Adding Start, Stop, Reset button for timer - Stack Overflow

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I have this count-up timer code and want to add start, stop and reset button. It start right at the page load.

<script type="text/javascript">
    var timerVar = setInterval(countTimer, 1000);
    var totalSeconds = 0;

    function countTimer() {
       ++totalSeconds;
       var hour = Math.floor(totalSeconds /3600);
       var minute = Math.floor((totalSeconds - hour*3600)/60);
       var seconds = totalSeconds - (hour*3600 + minute*60);

       document.getElementById("hour").innerHTML =hour;
       document.getElementById("minute").innerHTML =minute;
       document.getElementById("seconds").innerHTML =seconds;
    }
</script>

I have this count-up timer code and want to add start, stop and reset button. It start right at the page load.

<script type="text/javascript">
    var timerVar = setInterval(countTimer, 1000);
    var totalSeconds = 0;

    function countTimer() {
       ++totalSeconds;
       var hour = Math.floor(totalSeconds /3600);
       var minute = Math.floor((totalSeconds - hour*3600)/60);
       var seconds = totalSeconds - (hour*3600 + minute*60);

       document.getElementById("hour").innerHTML =hour;
       document.getElementById("minute").innerHTML =minute;
       document.getElementById("seconds").innerHTML =seconds;
    }
</script>

• javascript
• html
• button
• timer
• counter

Share Improve this question Follow asked Aug 22, 2017 at 4:19 KryptoNeko9KryptoNeko9 3311 gold badge11 silver badge44 bronze badges 2

• Can you show us your attempt on adding the buttons? – maazadeeb Commented Aug 22, 2017 at 4:24
• Possible duplicate of Adding start, stop, and reset buttons for a timer – sheplu Commented Aug 22, 2017 at 5:26

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3 Answers 3

Sorted by: Reset to default 5

It's just some simple manipulation of hour, minute and seconds and making use of clearInterval and setInterval. In my snipper, reset won't stop the timer, but it's easy to make that happen by a few lines of code.

window.onload = () => {
  let hour = 0;
  let minute = 0;
  let seconds = 0;
  let totalSeconds = 0;
  
  let intervalId = null;
  
  function startTimer() {
    ++totalSeconds;
    hour = Math.floor(totalSeconds /3600);
    minute = Math.floor((totalSeconds - hour*3600)/60);
    seconds = totalSeconds - (hour*3600 + minute*60);

    document.getElementById("hour").innerHTML =hour;
    document.getElementById("minute").innerHTML =minute;
    document.getElementById("seconds").innerHTML =seconds;
  }

  document.getElementById('start-btn').addEventListener('click', () => {
    intervalId = setInterval(startTimer, 1000);
  })
  
  document.getElementById('stop-btn').addEventListener('click', () => {
    if (intervalId)
      clearInterval(intervalId);
  });
  
   
  document.getElementById('reset-btn').addEventListener('click', () => {
     totalSeconds = 0;
     document.getElementById("hour").innerHTML = '0';
     document.getElementById("minute").innerHTML = '0';
     document.getElementById("seconds").innerHTML = '0';
  });
}

<div>Hour: <span id="hour"></span></div>
<div>Minute: <span id="minute"></span></div>
<div>Second: <span id="seconds"></span></div>

<button id="start-btn">Start</button>
<button id="stop-btn">Stop</button>
<button id="reset-btn">Reset</button>

Duplicate of Adding start, stop, and reset buttons for a timer

but just because there is not the HTML part, there is the full answer (html + js thanks to @closure )

(function() {
  "use strict";
  var secondsLabel = document.getElementById('seconds'),
  minutesLabel = document.getElementById('minutes'), 
  hoursLabel = document.getElementById('hours'), totalSeconds = 0, 
  startButton = document.getElementById('start'), 
  stopButton = document.getElementById('stop'), 
  resetButton = document.getElementById('reset'), timer = null;

  startButton.onclick = function() {
    if (!timer) {
      timer = setInterval(setTime, 1000);
    }
  };

  stopButton.onclick = function() {
    if (timer) {
      clearInterval(timer);
      timer = null;
    }
  };

  resetButton.onclick = function() {
    if (timer) {
      totalSeconds = 0;
      stop();
    }
  };

  function setTime() {
    totalSeconds++;
    secondsLabel.innerHTML = pad(totalSeconds % 60);
    minutesLabel.innerHTML = pad(parseInt(totalSeconds / 60));
    hoursLabel.innerHTML = pad(parseInt(totalSeconds / 3600))
  }

  function pad(val) {
    var valString = val + "";
    if (valString.length < 2) {
      return "0" + valString;
    } else {
      return valString;
    }
  }

})();

<p id='seconds'></p>
<p id='minutes'></p>
<p id='hours'></p>

<button id='start'>start</button>
<button id='stop'>stop</button>
<button id='reset'>reset</button>

//DOM CACHE
const startBtn = document.querySelector("#start-btn")
const stopBtn = document.querySelector("#stop-btn")
const resetBtn = document.querySelector("#reset-btn")
var minDigits = document.getElementById("min");
var secDigits = document.getElementById("sec");

//INITIALIZING VARIABLES
var hrs = 0;
var mins = 0;
var secs = 0;
var countSec = 0;
var timerVar = null;

//FUNCTIONS=============
function startCounter() {
    ++countSec;

    hrs = Math.floor(countSec /3600);
    mins = Math.floor((countSec - hrs*3600)/60);
    secs = countSec - (hrs*3600 + mins*60);

    if (secs < 10) {
        secDigits.innerHTML = "0" + secs;
    }  else { secDigits.innerHTML = secs; }

    minDigits.innerHTML = "0" + mins;   
}

startBtn.addEventListener('click', () => {
    timerVar = setInterval(startCounter, 1000);
})

stopBtn.addEventListener('click', () => {
    if (timerVar)
    clearInterval(timerVar);
});

resetBtn.addEventListener('click', () => {
    countSec = 0;
    secDigits.innerHTML = "00";
    minDigits.innerHTML = "00";
    clearInterval(timerVar);
});

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <title>Clock JS</title>
</head>
<body>
    <div class="container">
        <header>
            <h1>SIMPLE COUNTER</h1>
            <p>At A Time No Time To Check Time</p>
        </header>

        <div class="clock-face">
            <div class="digital-time"></div>
            <div class="greeting"></div>
            
            <div class="screen">
                <h1 class="digits">
                    <span id="min" class="minutes">00</span>:<span id="sec" class="seconds">00</span>
                </h1>
            </div>
            
            <div class="clock-dial">
                <button id="start-btn">start</button>
                <button id="stop-btn">stop</button>
                <button id="reset-btn">reset</button>
            </div>
        </div>
    </div>
    

    <script src="app.js" charset="utf-8"></script>
</body>
</html>

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