How to Add a Count Down Timer to React Native App

In one of my mobile apps, I needed to add a count down timer – which counts back from a specified time to zero time. I was preparing to create the same from the scratch until I saw this new third-party library named react native countdown timer.

Even though the react native library is relatively new, I choose it instead of reinventing the wheel. The timer component is easy to implement as well as customize. ‘

All you have to do is
npm install –save react-native-timer-countdown

Following is the example code to implement countdown timer in react native. For more details, you can check the official page.

import React from "react";
import { StyleSheet, View } from "react-native";
import TimerCountdown from "react-native-timer-countdown";

const App = () => (
  <View style={styles.container}>
    <TimerCountdown
      initialMilliseconds={1000 * 60}
      onTick={(milliseconds) => console.log("tick", milliseconds)}
      onExpire={() => console.log("complete")}
      formatMilliseconds={(milliseconds) => {
        const remainingSec = Math.round(milliseconds / 1000);
        const seconds = parseInt((remainingSec % 60).toString(), 10);
        const minutes = parseInt(((remainingSec / 60) % 60).toString(), 10);
        const hours = parseInt((remainingSec / 3600).toString(), 10);
        const s = seconds < 10 ? '0' + seconds : seconds;
        const m = minutes < 10 ? '0' + minutes : minutes;
        let h = hours < 10 ? '0' + hours : hours;
        h = h === '00' ? '' : h + ':';
        return h + m + ':' + s;
      }}
      allowFontScaling={true}
      style={{ fontSize: 20 }}
    />
  </View>
);

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: "#fff",
    alignItems: "center",
    justifyContent: "center"
  }
});

export default App;