A nice and accurate Javascript count-up/countdown timer.

Based on Tock by Mr Chimp and an idea by James Edwards.

License: MIT

• Pure Javascript, no dependencies.
• Self-correcting time based on the system clock.
• Count-up/countdown.
• Custom intervals and starting times.
• Start, stop, resume and reset.
• Callbacks: onTick(), onComplete(), onStart(), onStop() and onReset().
• Flexible time formatting.

Javascript's iteration timers using setInterval() or setTimeout() are not realiable enough. They create a difference between the iterated time and the real time. That difference can be compensated by using the actual time to adjust the timer.

These examples made by James Edwards illustrates the differences: http:https://www.sitepoint.com/examples/timeradjust/examples.html

Tock.js is not a full widget for a website, it is a timer library. You can use it either to display the result on screen or to make things work in the backend.

Let's see an example:

<span id="time">0</span>
<button id="start">Start</button>
<button id="stop">Stop</button>
<button id="reset">Reset</button>

var timer = new Tock(options);

The options parameter allows to customize the timer easily. All of them are optional, of course.

var options = {
  countdown: true,
  startTime: 10000
  interval: 15,
  onTick: function() {/* Some code... */},
  onComplete: function() {/* Some code... */},
  onStart: function() {/* Some code... */},
  onStop: function() {/* Some code... */},
  onReset: function() {/* Some code... */}
}

• countdown: boolean
  • If true, the timer will count down. Otherwise, it will count up.
  • Default: false.
• startTime: integer
  • The starting time in milliseconds. This should be set to a number greater than 0 when countdown is true.
  • Default: 0.
• interval: integer
  • The interval in milliseconds. This defines how often the timer will tick.
  • Default: 0.
• onTick: function
  • A function that will be called on every tick.
  • Default: A mockup function that will suggest to set a real one.
• onComplete: function
  • A function that will be called when a countdown reaches zero.
  • Default: A mockup function that will suggest to set a real one.
• onStart: function
  • A function that will be called when a timer is started.
  • Default: Dummy function.
• onStop: function
  • A function that will be called when a timer is stopped.
  • Default: Dummy function.
• onReset: function
  • A function that will be called when a timer is reset.
  • Default: Dummy function.

• start()
  • Starts the timer.
• stop()
  • Stops the timer. It is possible to resume the timer calling start() again.
• reset()
  • Resets the timer to startTime.
• lap(format)
  • Gets the current time in milliseconds.
  • The format parameter is optional, it is passed to the format() method.
• format(time, format)
  • Returns a time (milliseconds) in the specified format. (See the Time Format section)

On every tick (every interval milliseconds), onTick() will be called.

var options = {
  // some options...
  onTick: function() {
    // Pure javascript
    document.querySelector('#time').innerHTML = timer.lap();

    // Using jQuery/Zepto
    $('#time').text(timer.lap());
  }
}

When a countdown timer reaches zero, onComplete() will be called.

var options = {
  // some options...
  onComplete: function() {
    alert("Countdown complete!");
  }
}

When a timer starts, onStart() will be called.

var options = {
  // some options...
  onStart: function() {
    console.log("Start!");
  }
}

When a timer stop, onStop() will be called.

var options = {
  // some options...
  onStop: function() {
    console.log("Stop!");
  }
}

When a timer is reset, onReset() will be called.

var options = {
  // some options...
  onReset: function() {
    console.log("Reset!");
  }
}

The timer can be controlled easily with some buttons and events.

Start button:

// Pure Javascript
document.querySelector('#start').onclick = function() {
  timer.start();
});

// Using jQuery/Zepto
$('#start').on('click', function() {
  timer.start();
});

Stop button:

// Pure Javascript
document.querySelector('#stop').onclick = function() {
  timer.stop();
});

// Using jQuery/Zepto
$('#stop').on('click', function() {
  timer.stop();
});

Reset button:

// Pure Javascript
document.querySelector('#reset').onclick = function() {
  timer.reset();
});

// Using jQuery/Zepto
$('#reset').on('click', function() {
  timer.reset();
});

It is possible to set a "lap" button too:

// Pure Javascript
document.querySelector('#lap').onclick = function() {
  document.querySelector('#time').innerHTML += '<br />' + timer.lap();
});

// Using jQuery/Zepto
$('#lap').on('click', function() {
  $('#time').append('<br />' + timer.lap());
});

The format(time, format) method allows to customize the format of the given time (passed as milliseconds). It will replace the placeholders found in the format parameter, with the corresponding time information:

• {H}: Hours
• {h}: Hours (same as {H})
• {M}: Minutes
• {m}: Minutes (0 - 59)
• {S}: Seconds
• {s}: Seconds (0 - 59)
• {L}: Milliseconds (Default)
• {l}: Milliseconds (0 - 999)

Capital letters are raw values. This means that {M} displays the full number of minutes (i.e. 127 minutes), but {m} displays only the number of minutes elapsed since the last hour (7 in 127).

Double letters are used to retrieve the time with leading zeros. If {m} returns 7, {mm} will return 07.

Examples:

    Time: 3877012 (1 hour, 4 minutes, 37 seconds and 12 milliseconds)
    '{hh}:{mm}:{ss}.{ll}'        // 01:04:37.012
    '{MM}'                       // 64
    '{SS}.{ll}'                  // 3877.012
    '{MM} min and {ss} s'        // 64 min and 37 s
    '{h}:{m} vs {hh}:{mm}'       // 1:4 vs 01:04