/*
PHP navigation select dropdown menus are on form/submit.
This script lets only one URL be passed
by resetting the selectedIndex of the others so value="".
*/

// If a selection (change) is made on 1st menu, reset others to 0.
function zeroSelect1() {
	if (document.getElementById("producers").selectedIndex > 0)
  		document.getElementById("subjects").selectedIndex = 0;
  		document.getElementById("specials").selectedIndex = 0;
		document.getElementById("webworks").selectedIndex = 0;
}

// If a selection is made on 2nd menu, reset others to 0.
function zeroSelect2() {
	if (document.getElementById("subjects").selectedIndex > 0)
  		document.getElementById("producers").selectedIndex = 0;
 		document.getElementById("specials").selectedIndex = 0;
		document.getElementById("webworks").selectedIndex = 0;
}

// If a selection is made on 3rd menu, reset others to 0.
function zeroSelect3() {
	if (document.getElementById("specials").selectedIndex > 0)
  		document.getElementById("producers").selectedIndex = 0;
  		document.getElementById("subjects").selectedIndex = 0;
		document.getElementById("webworks").selectedIndex = 0;
}

// If a selection is made on 4th menu, reset others to 0.
function zeroSelect4() {
	if (document.getElementById("webworks").selectedIndex > 0)
  		document.getElementById("producers").selectedIndex = 0;
   		document.getElementById("specials").selectedIndex = 0;
  		document.getElementById("subjects").selectedIndex = 0;
}


// Function to add event listener to select elements.
	function load() { 
		var el1 = document.getElementById("producers"); 
		el1.addEventListener("change", zeroSelect1, false);
	
		var el2 = document.getElementById("subjects"); 
		el2.addEventListener("change", zeroSelect2, false);
		
		var el3 = document.getElementById("specials"); 
		el3.addEventListener("change", zeroSelect3, false);
		
		var el4 = document.getElementById("webworks"); 
		el4.addEventListener("change", zeroSelect4, false);
	} 

addLoadEvent(function() {
    load();
})