ReactJS Default props

``` ts
interface PageProps {
foo?: string;
}

export class PageComponent extends React.Component {
public static defaultProps: PageProps = {
foo: "default"
};

public render() {
return (
Hello, world
);
}
}
```

The issue contains only a TypeScript React component example and names no file, test, or requested outcome. First clarify whether it seeks documentation or a correction about defaultProps; then locate the relevant React and TypeScript book section and define the expected example.

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