Mandatory fields validation JS

//Mandatory fields
function ValidateRequired(txtItem,spanID)
{
document.getElementById(spanID).innerHTML='';
txtItem=document.getElementById(txtItem);
var txt = txtItem.value;
if(txt == '' txt == null txt == "")
{
document.getElementById(spanID).innerHTML= "Value required";
return false;
}
else
{
return true;
}
}