How to maintain a persistent state of the drop down?
I am making a simple web app that has drop down list in the first page in a form tags开发者_Go百科.
Now when I change the value in the dropdown the form is submitted. On the onchange I have made call to create a query string custom JS function of the selected Index.
Now I want the drop down list to maintain its state; keep the last selected value selected after submission.
You add the selected attribute with any (e.g. blank) value to the you want to keep selected.
The getQueryValue function is a bit unoptimized and would probably be better accomplished with a regular expression match to get the value, but I just typed it out like this so you could see what it was doing.
<html>
<head>
<script type="text/javascript">
function setSelections()
{
document.myForm.mySelect.value = getQueryValue("mySelect");
};
function getQueryValue(key)
{
var queryString = window.location.search.substring(1);
var queryParams = queryString.split("&");
for(var i = 0; i < queryParams.length; i++)
{
if(queryParams[i].indexOf("=") > 0)
{
var keyValue = queryParams[i].split("=");
if(keyValue[0] == key)
{
return keyValue[1];
}
}
}
return null;
}
</script>
</head>
<body onload="setSelections();">
<form name="myForm" action="" method="get">
<select id="mySelect" name="mySelect" onchange="document.myForm.submit();">
<option value="Opt1">Option 1</option>
<option value="Opt2">Option 2</option>
<option value="Opt3">Option 3</option>
<option value="Opt4">Option 4</option>
</select>
</form>
</body>
</html>
Depends on how your page is dealt with after submission, if it goes to a PHP/Perl or whatever language to rebuild the page, then put the drop down options into a script and loop through them.
Something like this is pretty common place
for($i = 0; $i < 10; $i++){
echo "<option value='{$i}' ";
($i == $_POST['dropdownname'])? echo "selected='selected'":"";
echo ">{$i}</option>";
}
You could pass a hidden form variable to the next posted page. Using a simple Javascript function that loops through the options of the selection drop-down list, if any of the options match the hidden value, then set its selected sttribute.
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