check empty fields and warn user to fill javascript

function check_field()
{

var myField=["lec_name","Name","lec_ic","IC"];
alert(myField.length);

for(x=0; x
{ var z = myField[x];
var y= myField[x+1];

if ( document.form1.elements[z].value =='' || document.form1.elements[z].value==null)
{
alert ("fill "+ y +" !");document.form1.elements[z].focus();return false;
}

x++;
}


}