JAVASCRIPT

react native scaling font

<Text
    numberOfLines={1}// add this
    adjustsFontSizeToFit// add this
    style={{textAlign:'center',fontSize:30}}
  >

react native font based on viewport dimensions

<View>
  <Text
    numberOfLines={1}
    adjustsFontSizeToFit
    style={{textAlign:'center',fontSize:30}}
  >
    {this.props.email}
  </Text>
</View>

responsive font size react native

import { Dimensions, Platform, PixelRatio } from 'react-native';

const {
  width,
  height,
} = Dimensions.get('window');

export function normalize(size, multiplier = 2) {
  const scale = (width / height) * multiplier;

  const newSize = size * scale;

  return Math.round(PixelRatio.roundToNearestPixel(newSize));
}