Play / Pause Realtime Countdown - After Effects Expression by Animoplex

PlayPauseCountdown.jsx

// Play / Pause Realtime Countdown - Created by Animoplex: www.animoplex.com
// Counts down a clock in realtime with the ability to play and pause the countdown with a checkbox
// NOTE: Expression will gradually slow down over duration of comp due to the while loop mechanic

src = effect("Checkbox Control")("Checkbox"); // play/pause control
dur = thisComp.frameDuration; // length of 1 frame
count = 300; // 5 minutes in seconds
t = 0;

function addZero(n) { // adds a zero to the end of numbers 0-9
  if (n < 10) {
    return "0" + n;
  } else {
    return n;
  }
}

while (t < time) {
  count -= src.valueAtTime(t) * dur; // adds value of all previous frames
  t += dur;
}

sec = count % 60; // seconds
min = count / 60; // minutes

addZero(Math.floor(min)) + ":" + addZero(Math.floor(sec)) // creates display output