get-query-params.js

function getQueryParams() {
    const queryString = document.location.search;

    if (!queryString) {
        return {};
    }

    return (
        // Strip the initial ?
        queryString.substring(1)
        // Split by parameter delimiter
        .split('&')
        // Split each parameter by key/value delimiter
        .map(segment => segment.split('=', 2))
        // Reduce to a key/value dictionary
        .reduce(
            (result, segment) => {
                const key = decodeURIComponent(segment[0]);
                let value = decodeURIComponent(segment[1]);

                // Translate plus to space and write it to the result
                value = value.replace(/\+/ig, ' ');
                result[key] = value;

                return result;
            },
            {},
        )
    );
}