catstodon/app/javascript/mastodon/components/animated_number.tsx

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import React, { useCallback, useState } from 'react';
import ShortNumber from './short_number';
import { TransitionMotion, spring } from 'react-motion';
import { reduceMotion } from '../initial_state';
const obfuscatedCount = (count: number) => {
if (count < 0) {
return 0;
} else if (count <= 1) {
return count;
} else {
return '1+';
}
};
type Props = {
value: number;
obfuscate?: boolean;
}
export const AnimatedNumber: React.FC<Props> = ({
value,
obfuscate,
})=> {
const [previousValue, setPreviousValue] = useState(value);
const [direction, setDirection] = useState<1|-1>(1);
if (previousValue !== value) {
setPreviousValue(value);
setDirection(value > previousValue ? 1 : -1);
}
const willEnter = useCallback(() => ({ y: -1 * direction }), [direction]);
const willLeave = useCallback(() => ({ y: spring(1 * direction, { damping: 35, stiffness: 400 }) }), [direction]);
if (reduceMotion) {
return obfuscate ? <>{obfuscatedCount(value)}</> : <ShortNumber value={value} />;
}
const styles = [{
key: `${value}`,
data: value,
style: { y: spring(0, { damping: 35, stiffness: 400 }) },
}];
return (
<TransitionMotion styles={styles} willEnter={willEnter} willLeave={willLeave}>
{items => (
<span className='animated-number'>
{items.map(({ key, data, style }) => (
<span key={key} style={{ position: (direction * style.y) > 0 ? 'absolute' : 'static', transform: `translateY(${style.y * 100}%)` }}>{obfuscate ? obfuscatedCount(data) : <ShortNumber value={data} />}</span>
))}
</span>
)}
</TransitionMotion>
);
};
export default AnimatedNumber;