React Native styling with conditional

There are two ways, by inline or calling a function:

1)

const styles = StyleSheet.create({
    green: {
        borderColor: 'green',
    },
    red: {
        borderColor: 'red',
    },
    
});

<TextInput style={[styles.otpBox, this.state.stateName ?
    styles.green :
    styles.red ]} />

getstyle(val) {
    if (val) {
        return { borderColor: 'red' };
    }
    else {
        return { borderColor: 'green' };
    }
}

<TextInput style={[styles.otpBox, this.getstyle(this.state.showValidatePOtp)]} />

Update your code as following:

<TextInput style={getTextStyle(this.state.touched, this.state.invalid)}></TextInput>

Then outside your class component, write:

getTextStyle(touched, invalid) {
 if(touched && invalid) {
  return {
    height: 40, backgroundColor: 'white', borderRadius: 5, padding: 10, borderWidth: 2, borderColor: 'red'
  }
 } else {
   return {
      height: 40, backgroundColor: 'white', borderRadius: 5, padding: 10
   }
 }
}

Use StyleSheet.create to do style composition like this,

make styles for text, valid text, and invalid text.

const styles = StyleSheet.create({
    text: {
        height: 40, backgroundColor: 'white', borderRadius: 5, padding: 10, 
    },
    textvalid: {
        borderWidth: 2,
    },
    textinvalid: {
        borderColor: 'red',
    },
});

and then group them together with an array of styles.

<TextInput
    style={[styles.text, touched && invalid ? styles.textinvalid : styles.textvalid]}
</TextInput>

For array styles, the latter ones will merge into the former one, with overwrite rule for the same keys.