function createRequestObject(){
	var request_o; //declare the variable to hold the object.
	var browser = navigator.appName; //find the browser name
	if(browser == "Microsoft Internet Explorer"){
		/* Create the object using MSIE's method */
		request_o = new ActiveXObject("Microsoft.XMLHTTP");
	}else{
		/* Create the object using other browser's method */
		request_o = new XMLHttpRequest();
	}
	return request_o; //return the object
}
var http = createRequestObject();


function search_avanzada() {
    
    if(document.getElementById('tit').value != "") {
        tit = 'tit=' + document.getElementById('tit').value + '&';
    }else {
        tit = '';
    }
    if(document.getElementById('opc_tit').value == "o") {
        opc_tit = 'opc_tit=' + document.getElementById('opc_tit').value + '&';   
    }else {
        opc_tit = '';
    }

    if(document.getElementById('aut').value != "") {
        aut = 'aut=' + document.getElementById('aut').value + '&';
    }else {
        aut = '';
    }
    if(document.getElementById('opc_aut').value == "o") {
        opc_aut = 'opc_aut=' + document.getElementById('opc_aut').value + '&';
    }else {
        opc_aut = '';
    }

    if(document.getElementById('edi').value != "") {
        edi = 'edi=' + document.getElementById('edi').value + '&';
    }else {
        edi = '';
    }
    if(document.getElementById('opc_edi').value == "o") {
        opc_edi = 'opc_edi=' + document.getElementById('opc_edi').value + '&';
    }else {
        opc_edi = '';
    }

    if(document.getElementById('isbn').value != "") {
        isbn = 'isbn=' + document.getElementById('isbn').value;
    }else {
        isbn = '';
    }

    if(document.getElementById('grp').value != "") {
        if(document.getElementById('gen').value != "") {
            grp = 'grp=' + document.getElementById('grp').value + '&';
            gen = 'gen=' + document.getElementById('gen').value;
        }else {
            grp = 'grp=' + document.getElementById('grp').value + '&';
            gen = '';
        }
    }else {
        grp = '';
        gen = '';
    }


    q = tit + opc_tit + aut + opc_aut + edi + opc_edi + isbn + grp + gen;
    //alert("q=?" + q);
    window.location = 'avanzada_resultados.php?' + q;
}


function busca_genero(grp) {

    if(grp == '') {
        document.getElementById('gen').disabled = true;
        return false;
    }
	
	function busca_genero_ajx() {
		if (http.readyState == 1) { //1: cargando
			//document.getElementById('id_departamento').disabled = true;
			document.getElementById('contGen').innerHTML = "cargando...";
		}
		if (http.readyState == 4) { //4: completado
			if (http.status == 200) { //200: OK
				res = http.responseText;
	   			document.getElementById('contGen').innerHTML = res;
	   			//document.getElementById('id_departamento').disabled = false;
	  		}
	  		else { //Se produjo un error
		   		alert("Error: " + http.statusText);
	  		}
	 	}
	}
	
	http.open('get', 'ajx_busca_genero.php?grp=' + grp);
	http.onreadystatechange = busca_genero_ajx;
	http.send(null);
}