Using JQuery or JavaScript, how do I do multiple selects on dropdown so, I can see multiple results in the page?

I have many DIV based contents in a page with a dropdown list. Right now, it shows everything, but, I want to choose an item from the dropdown list and it show the corresponding content based on the selection. Please make a correction to the function I'm using since it's not working: function toggleDIvDisplay() { var index = document.getElementById("App").selectedIndex.value; alert(index); var x = document.getElementById("maxLenght").value; for (i = 0; i < x; i++) { if(null != document.getElementById(i)) document.getElementById(i).style.visibility='block'; } document.getElementById(index).style.visibility='visible'; }