React <Countdown />

A customizable countdown component for React.

• Getting Started
• Motivation
• Examples
• Props
• API Reference
• Helpers
• License

Getting Started

You can either install the module via npm or yarn:

npm install react-countdown-now --save

yarn add react-countdown-now

Motivation

As part of a small web app at first, the idea was to separate the countdown component from the main package to combine general aspects of the development with React, testing with Jest and more things that relate to publishing a new Open Source project.

Examples

Here are some examples which you can try directly online. You can also clone this repo and explore some more examples in there by running yarn start within the examples folder.

Basic Usage

A very simple and minimal example of how to set up a countdown which counts down from 10 seconds.

import React from 'react';
import ReactDOM from 'react-dom';
import Countdown from 'react-countdown-now';

ReactDOM.render(
  ,
  document.getElementById('root')
);

Live Demo

Custom & Conditional Rendering

In case you want to change the output of the component, or want to signal that the countdown's work is done, you can do this by either using the onComplete callback, a custom renderer, or by specifying a React child within ``, which will only be shown once the countdown is complete.

Using a React Child for the Completed State

import React from 'react';
import ReactDOM from 'react-dom';
import Countdown from 'react-countdown-now';

// Random component
const Completionist = () =&gt; <span>You are good to go!</span>;

ReactDOM.render(
  (
    
      
    
  ),
  document.getElementById('root')
);

Live Demo

Custom Renderer with Completed Condition

import React from 'react';
import ReactDOM from 'react-dom';
import Countdown from 'react-countdown-now';

// Random component
const Completionist = () =&gt; <span>You are good to go!</span>;

// Renderer callback with condition
const renderer = ({ hours, minutes, seconds, completed }) =&gt; {
  if (completed) {
    // Render a completed state
    return ;
  } else {
    // Render a countdown
    return <span>{hours}:{minutes}:{seconds}</span>;
  }
};

ReactDOM.render(
  ,
  document.getElementById('root')
);

Live Demo

Countdown in Milliseconds

Here is an example with a countdown of 10 seconds that displays the total time difference in milliseconds. In order to display the milliseconds appropriately, the intervalDelay value needs to be lower than 1000ms and a precision of 1 to 3 should be used. Last but not least, a simple renderer callback needs to be set up.

import React from 'react';
import ReactDOM from 'react-dom';
import Countdown from 'react-countdown-now';

ReactDOM.render(
   <div>{props.total}</div>}
  /&gt;,
  document.getElementById('root')
);

Live Demo

Props

Name	Type	Default	Description
date	Date	string	number
key	string	number	undefined
daysInHours	boolean	false	Days are calculated as hours
zeroPadTime	number	2	Length of zero-padded output, e.g.: 00:01:02
zeroPadDays	number	zeroPadTime	Length of zero-padded days output, e.g.: 01
controlled	boolean	false	Hands over the control to its parent(s)
intervalDelay	number	1000	Interval delay in milliseconds
precision	number	0	The precision on a millisecond basis
autoStart	boolean	true	Countdown auto-start option
children	any	null	A React child for the countdown's completed state
renderer	function	undefined	Custom renderer callback
now	function	Date.now	Alternative handler for the current date
onMount	function	undefined	Callback when component mounts
onStart	function	undefined	Callback when countdown starts
onPause	function	undefined	Callback when countdown pauses
onTick	function	undefined	Callback on every interval tick (controlled = false)
onComplete	function	undefined	Callback when countdown ends

date

The date prop is the only required one and can be a Date object, string, or timestamp in the future. By default, this date value gets compared with the current date, or a custom handler defined via now.

Valid values can be (and more):

• '2020-02-01T01:02:03' // Date time string format
• 1580518923000 // Timestamp in milliseconds
• new Date(1580518923000) // Date object

key

This is one of React's internal component props and is used to identify the component. However, we can leverage this behavior and use it to, for example, restart the countdown by passing in a new string or number.

Please see official React docs for more information about keys.

daysInHours

Defines whether the time of day should be calculated as hours rather than separated days.

controlled

Can be useful if the countdown's interval and/or date control should be handed over to the parent. In case controlled is true, the provided date will be treated as the countdown's actual time difference and not be compared to now anymore.

zeroPadTime

This option defaults to 2 in order to display the common format 00:00:00 instead of 0:0:0. If the value is higher than 2, only the hours part (see zeroPadDays for days) will be zero-padded while it stays at 2 for minutes as well as seconds. If the value is lower, the output won't be zero-padded like the example before is showing.

zeroPadDays

Defaults to zeroPadTime. Works the same way as zeroPadTime does, just for days.

intervalDelay

Since this countdown is based on date comparisons, the default value of 1000 milliseconds is probably enough for most scenarios and doesn't need to be changed.

However, if it needs to be more precise, the intervalDelay can be set to something lower - down to 0, which would, for example, allow showing the milliseconds in a more fancy way (currently only possible through a custom renderer).

precision

In certain cases, you might want to base off the calculations on a millisecond basis. The precision prop, which defaults to 0, can be used to refine this calculation. While the default value simply strips the milliseconds part (e.g.: 10123ms => 10000ms), a precision of 3 leads to 10123ms.

autoStart

Defines whether the countdown should start automatically or not. Defaults to true.

children

This component also considers the child that may live within the `` element, which, in case it's available, replaces the countdown's component state once it's complete. Moreover, an additional prop called countdown is set and contains data similar to what the renderer callback would receive. Here's an example that showcases its usage.

Please note that once a custom renderer is defined, the children prop will be ignored.

renderer(props)

The component's render output is very simple and depends on daysInHours: {days}:{hours}:{minutes}:{seconds}. If this doesn't fit your needs, a custom renderer callback can be defined to return a new React element. It receives an argument which consists of a time delta object (incl. formatted values) to help building your own representation of the countdown.

{ total, days, hours, minutes, seconds, milliseconds, completed }

The render props also contain the countdown's API as api prop as well as the passed in component props.

Please note that once a custom renderer is defined, the children prop will be ignored.

now

If the current datetime (determined via a reference to Date.now) is not the right thing to compare with for you, a reference to a custom function which returns a similar dynamic value could be provided as an alternative.

onMount

onMount is a callback and triggered when the countdown mounts. It receives the time delta object which is returned by calcTimeDelta.

onStart

onStart is a callback and triggered whenever the countdown is started (including first-run). It receives the time delta object which is returned by calcTimeDelta.

onPause

onPause is a callback and triggered every time the countdown is paused. It receives the time delta object which is returned by calcTimeDelta.

onTick

onTick is a callback and triggered every time a new period is started, based on what the intervalDelay's value is. It only gets triggered when the countdown's controlled prop is set to false, meaning that the countdown has full control over its interval. It receives the time delta object which is returned by calcTimeDelta.

onComplete

onComplete is a callback and triggered whenever the countdown ends. In contrast to onTick, the onComplete callback gets also triggered in case controlled is set to true. It receives the time delta object which is returned by calcTimeDelta.

API Reference

The countdown component exposes a simple API through the getApi() function that can be accessed via component ref. It is also part (api) of the render props passed into renderer if needed.

start()

Starts the countdown in case it is paused or needed when autoStart is set to false.

pause()

Pauses the running countdown. This only works as expected if the controlled prop is set to false because calcTimeDelta does calculate this offset time internally.

isPaused()

Returns a boolean for whether the countdown has been paused or not.

isCompleted()

Returns a boolean for whether the countdown has been completed or not.

Helpers

This module also exports 3 simple helper functions which can be utilized to build your own countdown custom renderer.

import Countdown, { zeroPad, calcTimeDelta, formatTimeDelta } from 'react-countdown-now';

zeroPad(value, [length = 2])

The zeroPad function works similar to other well-known pad-functions and takes 2 arguments into account. A value which can be a string or number, as well as a length parameter which defaults to 2 as you are most likely only going to use this function if you actually want to pad one of your values. Either returns a number if length equals 0, or the zero-padded string.

const renderer = ({ hours, minutes, seconds }) => (
  <span>
    {zeroPad(hours)}:{zeroPad(minutes)}:{zeroPad(seconds)}
  </span>
);

calcTimeDelta(date, [options])

calcTimeDelta calculates the time difference between a given end date and the current date (now). It returns, similar to the renderer callback, a custom object (also referred to as countdown time delta object) with the following time related data:

{ total, days, hours, minutes, seconds, milliseconds, completed }

This function accepts 2 arguments in total, only the first one is required.

date Date or timestamp representation of the end date. See date prop for more details.

The second argument (options) could be an optional object consisting of the following optional keys.

now = Date.now Alternative function for returning the current date, also see now.

precision = 0 The precision on a millisecond basis.

controlled = false Defines whether the calculated value is already provided as the time difference or not.

offsetTime = 0 Defines the offset time that gets added to the start time; only considered if controlled is false.

formatTimeDelta(delta, [options])

formatTimeDelta formats a given countdown time delta object. It returns the formatted portion of it, equivalent to:

{ days, hours, minutes, seconds }

This function accepts 2 arguments in total, only the first one is required.

delta Time delta object, e.g.: returned by calcTimeDelta.

options The options object consists of the following three component props and is used to customize the formatting of the delta object:

• daysInHours
• zeroPadTime
• zeroPadDays

License

MIT