React Native add bold or italics to single words in <Text> field

Question

You can use <Text> like a container for your other text components. This is example:

...
<Text>
  <Text>This is a sentence</Text>
  <Text style={{fontWeight: "bold"}}> with</Text>
  <Text> one word in bold</Text>
</Text>
...

Here is an example.

For a more web-like feel:

const B = (props) => <Text style={{fontWeight: 'bold'}}>{props.children}</Text>

<Text>I am in <B>bold</B> yo.</Text>

you can use https://www.npmjs.com/package/react-native-parsed-text

import ParsedText from 'react-native-parsed-text';
 
class Example extends React.Component {
  static displayName = 'Example';
 
  handleUrlPress(url) {
    LinkingIOS.openURL(url);
  }
 
  handlePhonePress(phone) {
    AlertIOS.alert(`${phone} has been pressed!`);
  }
 
  handleNamePress(name) {
    AlertIOS.alert(`Hello ${name}`);
  }
 
  handleEmailPress(email) {
    AlertIOS.alert(`send email to ${email}`);
  }
 
  renderText(matchingString, matches) {
    // matches => ["[@michel:5455345]", "@michel", "5455345"]
    let pattern = /\[(@[^:]+):([^\]]+)\]/i;
    let match = matchingString.match(pattern);
    return `^^${match[1]}^^`;
  }
 
  render() {
    return (
      <View style={styles.container}>
        <ParsedText
          style={styles.text}
          parse={
            [
              {type: 'url',                       style: styles.url, onPress: this.handleUrlPress},
              {type: 'phone',                     style: styles.phone, onPress: this.handlePhonePress},
              {type: 'email',                     style: styles.email, onPress: this.handleEmailPress},
              {pattern: /Bob|David/,              style: styles.name, onPress: this.handleNamePress},
              {pattern: /\[(@[^:]+):([^\]]+)\]/i, style: styles.username, onPress: this.handleNamePress, renderText: this.renderText},
              {pattern: /42/,                     style: styles.magicNumber},
              {pattern: /#(\w+)/,                 style: styles.hashTag},
            ]
          }
          childrenProps={{allowFontScaling: false}}
        >
          Hello this is an example of the ParsedText, links like http://www.google.com or http://www.facebook.com are clickable and phone number 444-555-6666 can call too.
          But you can also do more with this package, for example Bob will change style and David too. [email protected]
          And the magic number is 42!
          #react #react-native
        </ParsedText>
      </View>
    );
  }
}
 
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
 
  url: {
    color: 'red',
    textDecorationLine: 'underline',
  },
 
  email: {
    textDecorationLine: 'underline',
  },
 
  text: {
    color: 'black',
    fontSize: 15,
  },
 
  phone: {
    color: 'blue',
    textDecorationLine: 'underline',
  },
 
  name: {
    color: 'red',
  },
 
  username: {
    color: 'green',
    fontWeight: 'bold'
  },
 
  magicNumber: {
    fontSize: 42,
    color: 'pink',
  },
 
  hashTag: {
    fontStyle: 'italic',
  },
 
});

It is not in a text field as asked but wrapping separate text elements into a view would give the desired output. This can be used if you don't want to add another library into your project just for styling a few texts.

<View style={{flexDirection: 'row'}}>
 <Text style={{fontWeight: '700', marginRight: 5}}>Contact Type:</Text>
 <Text>{data.type}</Text>
</View>

Would result as follows

Use this react native library

To install

npm install react-native-htmlview --save

Basic Usage

 import React from 'react';
 import HTMLView from 'react-native-htmlview';

  class App extends React.Component {
  render() {
   const htmlContent = 'This is a sentence <b>with</b> one word in bold';

  return (
   <HTMLView
     value={htmlContent}
   />    );
  }
}

Supports almost all html tags.

For more advanced usage like

1. Link handling
2. Custom Element Rendering

View this ReadMe

You can also put a Text tag inside of another Text tag. The second text tag will inherit the styling of the first, but you maintain the ability to style it independently from its parent.

<Text style={styles.bold}>Level: 
    <Text style={styles.normal}>Easy</Text>
</Text>

//in your stylesheet...

  bold: {
    fontSize: 25,
    fontWeight: "bold",
    color: "blue",
  },
  normal: {
  // will inherit size and color attributes
    fontWeight: "normal",
  }