JS query param helper functions

js-query-param-helper-functions

/**
 * Insert or change a query param.
 *
 * See: http://stackoverflow.com/questions/486896/adding-a-parameter-to-the-url-with-javascript
 *
 * @param {string} key   - The query param key.
 * @param {string} value - The query param value.
 */
var setQueryParam = function( key, value ) {
	key   = encodeURI( key );
	value = encodeURI( value );

	var kvp = document.location.search.substr( 1 ).split( '&' );
	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( '=' );
	}

	if ( history.pushState ) {
		var newURL = window.location.protocol + "//" + window.location.host + window.location.pathname + '?' + kvp.join( '&' );
		window.history.pushState({
			path: newURL,
		}, '', newURL );
	}
};

/**
 * Return the value of a query param.
 *
 * See: http://stackoverflow.com/questions/901115/how-can-i-get-query-string-values-in-javascript
 *
 * @param {string} name - The query param key to return.
 *
 * @return {string}     - The query param value.
 */
var getQueryParam = function( name ) {
	name = name.replace( /[\[\]]/g, "\\$&" );

	var url     = window.location.href;
	var regex   = new RegExp( "[?&]" + name + "(=([^&#]*)|&|#|$)" );
	var results = regex.exec(url);

	if ( ! results ) {
		return null;
	}
	if ( ! results[2] ) {
		return '';
	}

	return decodeURIComponent( results[2].replace( /\+/g, " " ) );
};