The Button component

Button is such a common component that you will find yourself using it in any kind of app. Let's build a small like counter with up and down buttons:

// Chapter 2 / Example 7 / src / LikeCounter.js
class LikeCounter extends React.Component {
    state = {
        likeCount: 0
    }
    // like/unlike function to increase/decrease like count in state
    like = () => this.setState({likeCount: this.state.likeCount + 1})
    unlike = () => this.setState({likeCount: this.state.likeCount - 1})

    render = () => (
        <View style={styles.container}>
            <Button
                onPress={this.unlike}
                title="Unlike"
            />
            <Text style={styles.text}>{this.state.likeCount}</Text>
            <Button
                onPress={this.like}
                title="Like"
            />
        </View>
    );
}
// Styles omitted for clarity

Further modifications to this concept can implement upvotes/downvotes for comments or a star system for reviews.