Script to get the current query string variables and load them into the designated iframe (https://jsfiddle.net/dougblackjr/v41ztjes/4/)

iframeLoader.js

const iframeLoader = {
	baseUrl: 'http://interimhh.hrmdirect.com/employment/job-openings.php?search=true&',
	queryStrings: [
		'dept',
		'city',
		'state',
		'cust_sort1'
	],
	init: function(id) {

		let url = this.baseUrl

		let self = this

		this.queryStrings.forEach(function(q) {

			const a = self.getParameterByName(q)

			if(a) {
				url += q + '=' + a + '&'
			}

		})

		if(url[url.length - 1] == '&') {
			url = url.substring(0, url.length - 1);
		}

		this.domReady(function() {
			document.getElementById(id).src = url
		})

	},
	domReady: function (fn) {

		document.addEventListener("DOMContentLoaded", fn);

		if (document.readyState === "interactive" || document.readyState === "complete" ) {

			fn();

		}

	},
	getParameterByName: function (name) {

		url = window.location.href;

		name = name.replace(/[\[\]]/g, '\\$&');

		var regex = new RegExp('[?&]' + name + '(=([^&#]*)|&|#|$)'),
	        results = regex.exec(url);

	    if (!results) return '-1';

	    if (!results[2]) return '-1';

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

	}
}

FIDDLE HERE: https://jsfiddle.net/dougblackjr/v41ztjes/4/