These functions include inserting a URL parameter, getting value from a URL parameter, and parsing query string

url-functions.js

/**
 * Insert Parameter in URL
 *
 * Dynamically insert or update a parameter in the URL.
 *
 * @param {string} key parameter name
 * @param {string} value parameter value
 * @param {string} base set a custom URL base.
 * @param {boolean} historyUpdate defines if it update the URL without reloading the page
 */
const insertParamToUrl = function( key, value, base = '', historyUpdate = false ) {
  // Check if both key exists.
  var kvp = document.location.search.substr(1).split('&');

  if ( key ) {
    key = encodeURI( key );
    value = value ? encodeURI( value ) : '';


    var i = kvp.length; var x;
    while ( i-- ) {
      x = kvp[i].split( '=' );

      if ( x[0] == key ) {
        x[1] = value;
        kvp[i] = x.join( '=' );
        break;
      }
    }

    if ( i < 0 ) {
      kvp[kvp.length] = [key, value].join('=');
    }
  }

  // this will reload the page, it's likely better to store this until finished
  // document.location.search = kvp.join( '&' );
  var urlBase = window.location.origin + ( base ? base : window.location.pathname );
  var newUrl = urlBase + '?' + kvp.join( '&' ) + window.location.hash;

  if ( historyUpdate ) {
    window.history.replaceState( null, null, newUrl );
  }

  return newUrl;
}

/**
 * Parse Query String
 *
 * @param {string} query
 */
const parse_query_string = function( query ) {
  var vars = query.split("&");
  var query_string = {};

  for ( var i = 0; i < vars.length; i++ ) {
    var pair = vars[i].split("=");
    var key = decodeURIComponent(pair[0]);
    var value = decodeURIComponent(pair[1]);
    // If first entry with this name
    if (typeof query_string[key] === "undefined") {
      query_string[key] = decodeURIComponent(value);
      // If second entry with this name
    } else if (typeof query_string[key] === "string") {
      var arr = [query_string[key], decodeURIComponent(value)];
      query_string[key] = arr;
      // If third or later entry with this name
    } else {
      query_string[key].push(decodeURIComponent(value));
    }
  }

  return query_string;
}

/**
 * Get URL Parameter
 *
 * Usage:
 * var searchText = getUrlParameter( 'search' );
 *
 * @param  {string} sParam    parameter name, e.g., "search"
 * @param  {string} link      (optional) if you want to get the parameter from
 *                            a different URL then current page url.
 * @return {multiple}         returns the 'value' of parameter
 */
var getUrlParameter = function( sParam, link ) {
  var sPageURL = ( link ) ? link : decodeURIComponent(window.location.search.substring(1)),
      sURLVariables = sPageURL.split('&'),
      sParameterName,
      i;

  for ( i = 0; i < sURLVariables.length; i++ ) {
    sParameterName = sURLVariables[i].split('=');

    if (sParameterName[0] === sParam) {
        return sParameterName[1] === undefined ? true : sParameterName[1];
    }
  }
}