React + React Router, handling all links to open in new tab

You can create a wrapper component, that decides whether or not the link is external, and renders the <a> element with appropriate props.

Implementing it in that way you'll improve the reusability.

Why the reusability will be improved? Here a few examples:

• Imagine that in the beginning you have 20 external URLs and you manually manage their props (without wrapper component). Later you decide to add a new prop to each one of the external urls and you have to manually change it to 20 places.
• URLs come from an API response and you have to list them in more than one component. Wihout a wrapper component - you will repeat the logic of deciding whether the URL is external or not.

Here is an example with a wrapper component:

// Define the Link wrapper component
class Link extends React.Component{
    constructor(props) {
        super(props);
        this.state = {
            target: props.target || this.getTarget(props.href)
        };
    }

    getTarget(url) {
        const siteDomain = 'stackoverflow.com';
        const isExternal = (url.indexOf(siteDomain) === -1);

        if (isExternal) return '_blank';

        return '_self';
    }

    render() {
        const props = Object.assign(this.props, ...this.state);
        return <a {...props}>{this.props.children}</a>
    }
}

// Use the Link wrapper
class Example extends React.Component{
    render() {
        return <Link href="http://google.com/">This is an external link</Link>
    }
}

External links should be defined as a elements, not Link elements, so that you can use target="_blank" to open the link in a new tab.