This method allows us to catch the JavaScript errors in React Components. We can log those errors and display another fallback UI instead of the component tree that crashed.

Now we have a clear idea about component methods that are available in React Components.

Observe the following JavaScript code snippet:

<section>
<h2>My First Example</h2>
</section>
<script>
 var root = document.querySelector('section').createShadowRoot();
 root.innerHTML = '<style>h2{ color: red; }</style>' +'<h2>Hello World!</h2>';
</script>

Now, observe the following ReactJS code snippet:

var sectionStyle = {
 color: 'red'
};
var MyFirstExample = React.createClass({
render: function() {
 return (<section><h2 style={sectionStyle}>
 Hello World!</h2></section>
 )}
})
ReactDOM.render(<MyFirstExample />, renderedNode);

Now, after observing the preceding examples of React and JavaScript, we will have a clear idea of normal HTML encapsulation and ReactJS custom HTML tags.