React - How to get parameter value from query string?

React Router v4 and React Router v5, generic

React Router v4 does not parse the query for you any more, but you can only access it via this.props.location.search (or useLocation, see below). For reasons see nbeuchat's answer.

E.g. with qs library imported as qs you could do

qs.parse(this.props.location.search, { ignoreQueryPrefix: true }).__firebase_request_key

Another library would be query-string. See this answer for some more ideas on parsing the search string. If you do not need IE-compatibility you can also use

new URLSearchParams(this.props.location.search).get("__firebase_request_key")

For functional components you would replace this.props.location with the hook useLocation. Note, you could use window.location.search, but this won't allow to trigger React rendering on changes. If your (non-functional) component is not a direct child of a Switch you need to use withRouter to access any of the router provided props.

React Router v3

React Router already parses the location for you and passes it to your RouteComponent as props. You can access the query (after ? in the url) part via

this.props.location.query.__firebase_request_key

If you are looking for the path parameter values, separated with a colon (:) inside the router, these are accessible via

this.props.match.params.redirectParam

This applies to late React Router v3 versions (not sure which). Older router versions were reported to use this.props.params.redirectParam.

General

nizam.sp's suggestion to do

console.log(this.props)

will be helpful in any case.

React Router v4

Using component

<Route path="/users/:id" component={UserPage}/> 

this.props.match.params.id

The component is automatically rendered with the route props.

Using render

<Route path="/users/:id" render={(props) => <UserPage {...props} />}/> 

this.props.match.params.id

Route props are passed to the render function.

React Router v3

With React Router v3, you can get query-string from this.props.location.search (?qs1=naisarg&qs2=parmar). For example, with let params = queryString.parse(this.props.location.search), would give { qs1 : 'naisarg', qs2 : 'parmar'}

React Router v4

With React Router v4, the this.props.location.query does not exist anymore. You need to use this.props.location.search instead and parse the query parameters either by yourself or using an existing package such as query-string.

Example

Here is a minimal example using React Router v4 and the query-string library.

import { withRouter } from 'react-router-dom';
import queryString from 'query-string';
    
class ActivateAccount extends Component{
    someFunction(){
        let params = queryString.parse(this.props.location.search)
        ...
    }
    ...
}
export default withRouter(ActivateAccount);

Rational

The React Router's team rational for removing the query property is:

There are a number of popular packages that do query string parsing/stringifying slightly differently, and each of these differences might be the "correct" way for some users and "incorrect" for others. If React Router picked the "right" one, it would only be right for some people. Then, it would need to add a way for other users to substitute in their preferred query parsing package. There is no internal use of the search string by React Router that requires it to parse the key-value pairs, so it doesn't have a need to pick which one of these should be "right".

[...]

The approach being taken for 4.0 is to strip out all the "batteries included" kind of features and get back to just basic routing. If you need query string parsing or async loading or Redux integration or something else very specific, then you can add that in with a library specifically for your use case. Less cruft is packed in that you don't need and you can customize things to your specific preferences and needs.

You can find the full discussion on GitHub.