Collapsible text using reanimated

CollapsibleText.tsx

import { useEffect, useRef } from "react";
import { View } from "react-native";

import Animated, {
  useAnimatedStyle,
  useSharedValue,
} from "react-native-reanimated";

// Example
export default function App() {
  return (
    <CollapsibleText collapsedNumberOfLines={4}>
      Lorem Ipsum is simply text of the printing and typesetting industry. Lorem
      Ipsum has been the industry's standard dummy text ever since the 1500s,
      when an unknown printer took a galley of type and scrambled it to make a
      type specimen book. It has survived not only five centuries, but also the
      leap into electronic typesetting, remaining essentially unchanged. It was
      popularised in the 1960s with the release of Letraset sheets containing
      Lorem Ipsum passages, and more recently with desktop publishing software
      like Aldus PageMaker including versions of Lorem Ipsum.
    </CollapsibleText>
  );
}

const CollapsibleText = (props: {
  children: string;
  collapsedNumberOfLines: number;
}) => {
  const { children, collapsedNumberOfLines } = props;
  const expandedTextHeight = useSharedValue(0);
  const collapsedTextHeight = useSharedValue(0);
  const containerViewHeight = useSharedValue(0);

  const textStyle = useAnimatedStyle(() => {
    return {
      opacity: collapsedTextHeight.value ? 1 : 0,
      flex: 1,
    };
  }, []);

  const readMoreStyle = useAnimatedStyle(() => {
    return {
      opacity: containerViewHeight.value === collapsedTextHeight.value ? 1 : 0,
      fontWeight: "bold",
    };
  }, []);

  const readLessStyle = useAnimatedStyle(() => {
    return {
      opacity: containerViewHeight.value === expandedTextHeight.value ? 1 : 0,
      fontWeight: "bold",
    };
  }, []);

  const containerViewStyle = useAnimatedStyle(() => {
    return {
      height: containerViewHeight.value,
      overflow: "hidden",
      // Use flexWrap: "wrap" if you don't want words to be cut off
      // flexWrap: "wrap",
      flexDirection: "row",
    };
  }, []);

  useEffect(() => {
    // reset
    containerViewHeight.value = 0;
    expandedTextHeight.value = 0;
    collapsedTextHeight.value = 0;
  }, [
    children,
    collapsedNumberOfLines,
    expandedTextHeight,
    collapsedTextHeight,
    containerViewHeight,
  ]);

  return (
    <Animated.View
      style={containerViewStyle}
      onTouchEnd={() => {
        if (containerViewHeight.value === expandedTextHeight.value) {
          containerViewHeight.value = collapsedTextHeight.value;
        } else {
          containerViewHeight.value = expandedTextHeight.value;
        }
      }}
    >
      <Animated.Text
        style={textStyle}
        onTextLayout={(e) => {
          if (collapsedTextHeight.value === 0) {
            let expandedHeight = 0;
            let collapsedHeight = 0;
            for (let i = 0; i < e.nativeEvent.lines.length; i++) {
              expandedHeight += e.nativeEvent.lines[i].height;
              if (
                i <=
                Math.min(
                  collapsedNumberOfLines - 1,
                  e.nativeEvent.lines.length - 1
                )
              ) {
                collapsedHeight += e.nativeEvent.lines[i].height;
              }
            }
            expandedTextHeight.value = expandedHeight;
            collapsedTextHeight.value = collapsedHeight;
            containerViewHeight.value = collapsedHeight;
          }
        }}
      >
        {children}
        <Animated.Text style={readLessStyle}> less</Animated.Text>
      </Animated.Text>
      <View
        style={{
          justifyContent: "flex-end",
          height: "100%",
        }}
      >
        <Animated.Text style={readMoreStyle}>... more</Animated.Text>
      </View>
    </Animated.View>
  );
};