The children prop in React JS is a special prop that is automatically passed to every component. It can be used to render the content included between the opening and closing tags when invoking a component.

To add props.children inside opening and closing tags in React JS with children="xyz" attribute, you can use the following syntax:

<MyComponent children="xyz"></MyComponent>

The MyComponent component will then render the content of the children prop, which is the string xyz in this case.

Here is an example of how to use props.children with children="xyz" attribute:

const MyComponent = ({ children }) => {
  return (
    <div>
      {children}
    </div>
  );
};

export default MyComponent;

In this example, the MyComponent component takes a children prop and renders the content of the prop. The children prop can be anything, including a string, a number, an object, or an array.

In the example above, the children prop is set to the string xyz. This means that the MyComponent component will render the string xyz.

You can also use the children prop to render child components. For example, the following code will render a div element with the text "Hello, world!" inside it:

const MyComponent = ({ children }) => {
  return (
    <div>
      {children}
    </div>
  );
};

export default MyComponent;

<MyComponent>
  <div>Hello, world!</div>
</MyComponent>

In this example, the children prop is set to a div element with the text "Hello, world!" inside it. This means that the MyComponent component will render the div element with the text "Hello, world!" inside it.

The children prop is a powerful tool that can be used to render arbitrary content inside React components.