I will show you the HTML code, this code consist of two dropdownlist /
combo box (two <select> element) with the second <select>
element disabled and will be enabled if we choose something from the
first <select> element. Here the HTML code (dnmddl.htm):
HTML FORM
Don’t be afraid, eventhough the Javascript code look a bit large but what is done by this code only initialize the array with specified value and fill it to the second dropdownlist element (slc_target). This is the Javascript code (dynamicddl.js):
JAVASCRIPT:
HTML FORM
<!doctype html public "-//w3c//dtd html 3.2//en">
<html>
<head>
<title>(Type a title for your page here)</title>
<script language="javascript" src="list.js"></script>
</head>
<body bgcolor="#ffffff" text="#000000" link="#0000ff" vlink="#800080" alink="#ff0000" onLoad="fillCategory();">
<FORM name="drop_list" action="yourpage.php" method="POST" >
<SELECT NAME="Category" onChange="SelectSubCat();" >
<Option value="">Category</option>
</SELECT>
<SELECT id="SubCat" NAME="SubCat">
<Option value="">SubCat</option>
</SELECT>
</form>
</body>
</html>
<html>
<head>
<title>(Type a title for your page here)</title>
<script language="javascript" src="list.js"></script>
</head>
<body bgcolor="#ffffff" text="#000000" link="#0000ff" vlink="#800080" alink="#ff0000" onLoad="fillCategory();">
<FORM name="drop_list" action="yourpage.php" method="POST" >
<SELECT NAME="Category" onChange="SelectSubCat();" >
<Option value="">Category</option>
</SELECT>
<SELECT id="SubCat" NAME="SubCat">
<Option value="">SubCat</option>
</SELECT>
</form>
</body>
</html>
Don’t be afraid, eventhough the Javascript code look a bit large but what is done by this code only initialize the array with specified value and fill it to the second dropdownlist element (slc_target). This is the Javascript code (dynamicddl.js):
JAVASCRIPT:
function fillCategory(){
// this function is used to fill the category list on load
addOption(document.drop_list.Category, "Fruits", "Fruits", "");
addOption(document.drop_list.Category, "Games", "Games", "");
addOption(document.drop_list.Category, "Scripts", "Scripts", "");
}
function SelectSubCat(){
// ON selection of category this function will work
removeAllOptions(document.drop_list.SubCat);
addOption(document.drop_list.SubCat, "", "SubCat", "");
if(document.drop_list.Category.value == 'Fruits'){
addOption(document.drop_list.SubCat,"Mango", "Mango");
addOption(document.drop_list.SubCat,"Banana", "Banana");
addOption(document.drop_list.SubCat,"Orange", "Orange");
}
if(document.drop_list.Category.value == 'Games'){
addOption(document.drop_list.SubCat,"Cricket", "Cricket");
addOption(document.drop_list.SubCat,"Football", "Football");
addOption(document.drop_list.SubCat,"Polo", "Polo", "");
}
if(document.drop_list.Category.value == 'Scripts'){
addOption(document.drop_list.SubCat,"PHP", "PHP");
addOption(document.drop_list.SubCat,"ASP", "ASP");
addOption(document.drop_list.SubCat,"Perl", "Perl");
}
}
function removeAllOptions(selectbox)
{
var i;
for(i=selectbox.options.length-1;i>=0;i--)
{
//selectbox.options.remove(i);
selectbox.remove(i);
}
}
function addOption(selectbox, value, text )
{
var optn = document.createElement("OPTION");
optn.text = text;
optn.value = value;
selectbox.options.add(optn);
}
// this function is used to fill the category list on load
addOption(document.drop_list.Category, "Fruits", "Fruits", "");
addOption(document.drop_list.Category, "Games", "Games", "");
addOption(document.drop_list.Category, "Scripts", "Scripts", "");
}
function SelectSubCat(){
// ON selection of category this function will work
removeAllOptions(document.drop_list.SubCat);
addOption(document.drop_list.SubCat, "", "SubCat", "");
if(document.drop_list.Category.value == 'Fruits'){
addOption(document.drop_list.SubCat,"Mango", "Mango");
addOption(document.drop_list.SubCat,"Banana", "Banana");
addOption(document.drop_list.SubCat,"Orange", "Orange");
}
if(document.drop_list.Category.value == 'Games'){
addOption(document.drop_list.SubCat,"Cricket", "Cricket");
addOption(document.drop_list.SubCat,"Football", "Football");
addOption(document.drop_list.SubCat,"Polo", "Polo", "");
}
if(document.drop_list.Category.value == 'Scripts'){
addOption(document.drop_list.SubCat,"PHP", "PHP");
addOption(document.drop_list.SubCat,"ASP", "ASP");
addOption(document.drop_list.SubCat,"Perl", "Perl");
}
}
function removeAllOptions(selectbox)
{
var i;
for(i=selectbox.options.length-1;i>=0;i--)
{
//selectbox.options.remove(i);
selectbox.remove(i);
}
}
function addOption(selectbox, value, text )
{
var optn = document.createElement("OPTION");
optn.text = text;
optn.value = value;
selectbox.options.add(optn);
}
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