You can do that by attaching an onclick handler to each of the divs. When it's called, the div element is passed to the handler/ From there, it's a simple matter of returning the id of the element that called the myOnclick function.
function myOnclick(el)
{
alert(el.id);
}
<div id = "1" onclick='myOnclick(this);' class ="Item">A</div>
<div id = "2" onclick='myOnclick(this);' class ="Item">B</div>
<div id = "3" onclick='myOnclick(this);'class ="Item">C</div>
<div id = "4" onclick='myOnclick(this);'class ="Item">D</div>