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In my react application I have a few parameters that the user comes to the application that provide some information about where they came from. Is there a way using react-router to preserve these query params throughout the entire application. meaning every time a route is changed Id like those query params to stay in the url. The only examples I've seen are passing query params between routes but not keeping them around for every route.

Answers

UPDATE

Solution for react-router v4 is available.

Solution for react-router v3:

I wrote this little history v3 (it's compatible with react-router v3) enhancer in Typescript. It will preserve given set of query parameters. Be careful - history passed to this function has to be enhanced with useQueries.

import {History, Location, LocationDescriptor} from 'history'

export default function preserveQueryHistory(history: History, queryParameters: string[]): History {
    function preserveQueryParameters(path: LocationDescriptor): Location {
        const location = history.createLocation(path)
        const currentQuery = history.getCurrentLocation().query
        for (let p of queryParameters) {
            const v = (currentQuery as any)[p]
            if (v) {
                location.query[p] = v
            }
        }
        return location
    }
    return {
        ...history,
        push(path: LocationDescriptor) {
            history.push(preserveQueryParameters(path))
        },
        replace(path: LocationDescriptor) {
            history.replace(preserveQueryParameters(path))
        }
    }
}

Now use it to create history:

import useQueries from 'history/lib/useQueries'
import createBrowserHistory from 'history/lib/createBrowserHistory'
import preserveQueryHistory from './preserveQueryHistory'

const history = preserveQueryHistory(useQueries(createBrowserHistory)(), ['language'])

And in react-router:

<Router history={history}>
...
</Router>

More ultimate solution with CreateHistory enhancer function that embeds applying useQueries enhancer and provides ability to inject custom History enhancer:

import {CreateHistory, History, HistoryOptions, HistoryQueries, Location, LocationDescriptor} from 'history'
import useQueries from 'history/lib/useQueries'

function preserveQueryParameters(history: History, queryParameters: string[], path: LocationDescriptor): Location {
    const location = history.createLocation(path)
    const currentQuery = history.getCurrentLocation().query
    for (let p of queryParameters) {
        const v = (currentQuery as any)[p]
        if (v) {
            location.query[p] = v
        }
    }
    return location
}

function enhanceHistory<H>(history: History & H, queryParameters: string[]): History & H {
    return Object.assign({}, history, {
        push(path: LocationDescriptor) {
            history.push(preserveQueryParameters(history, queryParameters, path))
        },
        replace(path: LocationDescriptor) {
            history.replace(preserveQueryParameters(history, queryParameters, path))
        }
    })
}

export function createPreserveQueryHistoryWithEnhancer<O, H, H2>(createHistory: CreateHistory<O, H>,
    queryParameters: string[], enhancer: (h: History) => History & H2): CreateHistory<O, H & H2 & HistoryQueries> {
    return function (options?: HistoryOptions & O): History & H & H2 & HistoryQueries {
        let h = enhancer(useQueries(createHistory)(options)) as History & H & H2 & HistoryQueries
        return enhanceHistory<H & H2 & HistoryQueries>(h, queryParameters)
    }
}

export function createPreserveQueryHistory<O, H>(createHistory: CreateHistory<O, H>,
    queryParameters: string[]): CreateHistory<O, H & HistoryQueries> {
    return createPreserveQueryHistoryWithEnhancer<O, H, {}>(createHistory, queryParameters, h => h)
}

export function preserveQueryHistoryWithEnhancer<H, H2>(history: History & H, queryParameters: string[],
    enhancer: (h: History) => History & H2): History & HistoryQueries & H & H2 {
    return createPreserveQueryHistoryWithEnhancer(
        function () {
            return history
        },
        queryParameters, enhancer)()
}

export function preserveQueryHistory<H>(history: History & H, queryParameters: string[]): History & HistoryQueries & H {
    return preserveQueryHistoryWithEnhancer<H, {}>(history, queryParameters, h => h)
}

Usage with syncHistoryWithStore react-router-redux v4 History enhancer:

import createBrowserHistory from 'history/lib/createBrowserHistory'
import {createPreserveQueryHistoryWithEnhancer} from './preserveQueryHistory'
import {syncHistoryWithStore} from 'react-router-redux'

const store = ...

const history = createPreserveQueryHistoryWithEnhancer(createBrowserHistory, ['language'], function (h: History) {
    return syncHistoryWithStore(h, store)
})()