React Query Params, Fragment

how do you extract search (also referred to as "query") parameters (=> ?something=somevalue  at the end of the URL)? How do you extract the fragment (=> #something  at the end of the URL)?

Query Params:

You can pass them easily like this:
<Link to="/my-path?start=5">Go to Start</Link>
or

<Link 
    to={{
        pathname: '/my-path',
        search: '?start=5'
    }}
    >Go to Start</Link>

React router makes it easy to get access to the search string: props.location.search .
But that will only give you something like ?start=5
You probably want to get the key-value pair, without the ?  and the = . Here's a snippet which allows you to easily extract that information:

componentDidMount() {
    const query = new URLSearchParams(this.props.location.search);
    for (let param of query.entries()) {
        console.log(param); // yields ['start', '5']
    }
}

URLSearchParams  is a built-in object, shipping with vanilla JavaScript. It returns an object, which exposes the entries()  method. entries()  returns an Iterator - basically a construct which can be used in a for...of...  loop (as shown above).
When looping through query.entries() , you get arrays where the first element is the key name (e.g. start ) and the second element is the assigned value (e.g. 5 ).

Fragment:

You can pass it easily like this:
<Link to="/my-path#start-position">Go to Start</Link>
or

<Link 
    to={{
        pathname: '/my-path',
        hash: 'start-position'
    }}
    >Go to Start</Link>

React router makes it easy to extract the fragment. You can simply access props.location.hash .