Compare text and highlight differences in react-native

Today i want to create a app in react-native that compare two string for first time it will be simple . For example

var str1 = "Hello there";
var str2 = "Hello";

I want to highlight a word that is different from the other text. And in example it is there. Something like online compare tools. So it will looks like

"There" word is with different background !

So i have no idea how to start. I tried with this code

const CustomText = (props) => {
    const text1 = props.str1.split(' ');
    const text2 = props.str2.split(' ');
    return <Text>{text1.map(text => {
      if (!text.includes(// here i should compare with other text)) {
        return <Text style={{ color: 'blue' }}>{text} </Text>;
      }
      return `${text} `;
    })}</Text>;
}

I dont knwo how to map this two string to compare each other . Thanks for helping ...