React Native component and hook to animate counting up or down to a number

by React Native Example

use-count-up

React/React Native component and hook to animate counting up or down to a number.

View Demo View Github

Key features

:trophy: Lighter implementation and smaller bundle size in comparison with similar feature solutions
:scroll: Support toLocaleString with fallback options
:flags: Declarative API (no more imperative calls to start() and update())
 :iphone:  React Native support for iOS and Android
:deciduous_tree: Tree-shakable (minified size further reduced by ~ 0.4kB when only the hook is used)
 :file_cabinet: Server-side rendering (SSR) compatibility

Installation

yarn add use-count-up

Demo

Check the React demo on CodeSandbox and React Native demo on Expo Snack to get started.

Component basic usage

import { CountUp } from 'use-count-up'

const MyComponent = () => <CountUp isCounting end={1320} duration={3.2} />

The CountUp component should be wrapped in a Text component when used in a React Native project like so:

import { Text } from 'react-native'
import { CountUp } from 'use-count-up'

const MyComponent = () => (
  <Text>
    <CountUp isCounting end={1320} duration={3.2} />
  </Text>
)

Hook basic usage

The hook accepts the same properties as the component. The usage for React and React Native is the same.

import { useCountUp } from 'use-count-up'

const MyComponent = () => {
  const { value } = useCountUp({
    isCounting: true,
    end: 1320,
    duration: 3.2,
  })

  return value
}

Props

The component and the hook accept the same props. They are fully interchangeable.

Prop Name Type Default Description
isCounting boolean false Play and pause counting animation
start number 0 Initial value
end number - Target value
duration number - Animation duration in seconds. Defaults to 2 seconds if end is set. If end isn't set, the animation will continue to Infinity.
decimalPlaces number - Number of decimal places after the decimal separator. Defaults to the max decimal places count from start and end
decimalSeparator string - Decimal separator character
thousandsSeparator string - Thousands separator character
prefix string - Static text before the value
suffix string - Static text after the value
shouldUseToLocaleString boolean false Indicates if toLocaleString should be used
toLocaleStringParams { locale, options } - Set toLocaleString locale and/or options by passing an object with locale and/or options keys. Read more here
fallbackPrefix string - Static text before the value to be used in case toLocaleString params are not supported
fallbackSuffix string - Static text after the value to be used in case toLocaleString params are not supported
autoResetKey number | string - Auto reset animation when the key changes. Works similarly to React key prop
easing string | function easeOutCubic Type: easeOutCubic | easeInCubic | linear | easing func
Easing function to control the animation progress
onComplete function - Type: () => void | {shouldRepeat: boolean, delay: number}
On complete handler. It can be used to repeat the animation by returning an object with the following props: shouldRepeat indicates if the animation should start over; delay specifies the delay before looping again in seconds.
formatter function - Type: (value: number) => number | string | node
A function that formats the output value. It has the highest priority so all other formating options are ignored
children function - Type: ({ value: number, reset: () => void }) => number | string | node
Render function to render the count up value. Used only by the component

Return values

The hook returns the current count up value and reset method to reset the animation.

import { useCountUp } from 'use-count-up'

const { value, reset } = useCountUp({ isCounting: true })

The component's children render function will receive as props the current count up value and reset method to reset the animation.

import { CountUp } from 'use-count-up'

const MyComponent = () => (
  <CountUp isCounting>{({ value, reset }) => value}</CountUp>
)

Why use toLocaleString

Number formatting varies per language group. For example, the number 3842.45 in German will be formatted as 3.842,45 whereas in British English it will be 3,842.45 (spot the different decimal and thousands separators). Number.toLocaleString() is a built-in JS method that returns a string with a language-sensitive representation of the number. The basic implementation of the method will detect the default locale that is set up on the user's computer and will format the number accordingly. The browser support for toLocaleString is incredibly good.

If you expect variance in the geographical/country distribution of your users, then this is a must. The simplest way to use toLocaleString with the Count up component or hook is to pass shouldUseToLocaleString: true like so:

import { CountUp } from 'use-count-up'

const MyComponent = () => (
  <CountUp isCounting end={1320} shouldUseToLocaleString />
)

toLocaleString method accepts an object with two parameters, locale and options, which allows further customization of the number value. Setting up the first parameter, locale, allows the use of a specific locale and fallback option. The second parameter, options, will let you format the value in a custom way. For example, you may choose to add a min and max number of decimal places, or set currency.

Keep in mind though that the locale and options arguments are not supported in all browsers. Despite that, the Count up library offers fallback options in case you need to support obsolete or niche browsers.

Setting up toLocaleString params without fallback options:

import { useCountUp } from 'use-count-up'

const MyComponent = () => {
  const { value } = useCountUp({
    isCounting: true,
    end: 1320,
    //enable toLocaleString and set params
    shouldUseToLocaleString: true,
    toLocaleStringParams: {
      locale: 'de-DE',
      options: { style: 'currency', currency: 'EUR', maximumFractionDigits: 2 },
    },
  })

  return value
}

Setting up toLocaleString params with fallback options:

import { useCountUp } from 'use-count-up'

const MyComponent = () => {
  const { value } = useCountUp({
    isCounting: true,
    end: 1320,
    shouldUseToLocaleString: true,
    toLocaleStringParams: {
      locale: 'de-DE',
      options: { style: 'currency', currency: 'EUR', maximumFractionDigits: 2 },
    },
    // fallback options
    decimalPlaces: 2,
    decimalSeparator: ',',
    thousandsSeparator: '.',
    fallbackSuffix: '€',
  })

  return value
}

Recipes

Reset animation on any prop change

Pass the value of the prop that should reset the animation to autoResetKey. The most common use case here is resetting the animation when the end value changes. Example:

import { CountUp } from 'use-count-up'

const MyComponent = ({ end }) => (
  <CountUp isCounting end={end} autoResetKey={end} />
)

Repeat animation on completion

Return from the onComplete handler an object with key shouldRepeat: true. Optionally the delay before repeating can be set. In the example below the animation will be repeated in 2 seconds

import { CountUp } from 'use-count-up'

const onComplete = () => {
  // do your stuff here
  return { shouldRepeat: true, delay: 2 }
}

const MyComponent = () => (
  <CountUp isCounting end={4378.2} onComplete={onComplete} />
)

Count up to infinity

Don't provide end and duration props. start prop can be set to any value

import { CountUp } from 'use-count-up'

const MyComponent = () => <CountUp isCounting start={1024.4} />

Count up/down n-seconds

Set the easing to "linear" and duration to the seconds it should count up/down. Here is an example of a 10-second count-down:

import { CountUp } from 'use-count-up'

const MyComponent = () => (
  <CountUp isCounting start={10} end={0} duration={10} easing="linear" />
)

GitHub