[javascript] Change the selected value of a drop-down list with jQuery

I have a drop-down list with known values. What I'm trying to do is set the drop down list to a particular value that I know exists using jQuery. Using regular JavaScript, I would do something like:

ddl = document.getElementById("ID of element goes here");
ddl.value = 2; // 2 being the value I want to set it too.

However, I need to do this with jQuery, because I'm using a CSS class for my selector (stupid ASP.NET client ids...).

Here are a few things I've tried:

$("._statusDDL").val(2); // Doesn't find 2 as a value.
$("._statusDDL").children("option").val(2) // Also failed.

How can I do it with jQuery?

Update

So as it turns out, I had it right the first time with:

$("._statusDDL").val(2);

When I put an alert just above it works fine, but when I remove the alert and let it run at full speed, I get the error

Could not set the selected property. Invalid Index

I'm not sure if it's a bug with jQuery or Internet Explorer 6 (I'm guessing Internet Explorer 6), but it's terribly annoying.

These solutions seem to assume that each item in your drop down lists has a val() value relating to their position in the drop down list.

Things are a little more complicated if this isn't the case.

To read the selected index of a drop down list, you would use this:

$("#dropDownList").prop("selectedIndex");

To set the selected index of a drop down list, you would use this:

$("#dropDownList").prop("selectedIndex", 1);

Note that the prop() feature requires JQuery v1.6 or later.

Let's see how you would use these two functions.

Supposing you had a drop down list of month names.

<select id="listOfMonths">
  <option id="JAN">January</option>
  <option id="FEB">February</option>
  <option id="MAR">March</option>
</select>

You could add a "Previous Month" and "Next Month" button, which looks at the currently selected drop down list item, and changes it to the previous/next month:

<button id="btnPrevMonth" title="Prev" onclick="btnPrevMonth_Click();return false;" />
<button id="btnNextMonth" title="Next" onclick="btnNextMonth_Click();return false;" />

And here's the JavaScript which these buttons would run:

function btnPrevMonth_Click() {
    var selectedIndex = $("#listOfMonths").prop("selectedIndex");
    if (selectedIndex > 0) {
        $("#listOfMonths").prop("selectedIndex", selectedIndex - 1);
    }
}
function btnNextMonth_Click() {
    //  Note:  the JQuery "prop" function requires JQuery v1.6 or later
    var selectedIndex = $("#listOfMonths").prop("selectedIndex");
    var itemsInDropDownList = $("#listOfMonths option").length;

    //  If we're not already selecting the last item in the drop down list, then increment the SelectedIndex
    if (selectedIndex < (itemsInDropDownList - 1)) {
        $("#listOfMonths").prop("selectedIndex", selectedIndex + 1);
    }
}

My site is also useful for showing how to populate a drop down list with JSON data:

http://mikesknowledgebase.com/pages/Services/WebServices-Page8.htm

<asp:DropDownList ID="DropUserType" ClientIDMode="Static" runat="server">
     <asp:ListItem Value="1" Text="aaa"></asp:ListItem>
     <asp:ListItem Value="2" Text="bbb"></asp:ListItem>
</asp:DropDownList>

ClientIDMode="Static"

$('#DropUserType').val('1');

I use an extend function to get client ids, like so:

$.extend({
    clientID: function(id) {
        return $("[id$='" + id + "']");
    }
});

Then you can call ASP.NET controls in jQuery like this:

$.clientID("_statusDDL")

Just a note - I've been using wildcard selectors in jQuery to grab items that are obfuscated by ASP.NET Client IDs - this might help you too:

<asp:DropDownList id="MyDropDown" runat="server" />

$("[id* = 'MyDropDown']").append("<option value='-1'>&nbsp;</option>"); //etc

Note the id* wildcard- this will find your element even if the name is "ctl00$ctl00$ContentPlaceHolder1$ContentPlaceHolder1$MyDropDown"

In my case I was able to get it working using the .attr() method.

$("._statusDDL").attr("selected", "");

After looking at some solutions, this worked for me.

I have one drop-down list with some values and I want to select the same value from another drop-down list... So first I put in a variable the selectIndex of my first drop-down.

var indiceDatos = $('#myidddl')[0].selectedIndex;

Then, I select that index on my second drop-down list.

$('#myidddl2')[0].selectedIndex = indiceDatos;

Note:

I guess this is the shortest, reliable, general and elegant solution.

Because in my case, I'm using selected option's data attribute instead of value attribute. So if you do not have unique value for each option, above method is the shortest and sweet!!

Another option is to set the control param ClientID="Static" in .net and then you can access the object in JQuery by the ID you set.

Just try with

$("._statusDDL").val("2");

and not with

$("._statusDDL").val(2);

I know this is a old question and the above solutions works fine except in some cases.

Like

<select id="select_selector">
<option value="1">Item1</option>
<option value="2">Item2</option>
<option value="3">Item3</option>
<option value="4" selected="selected">Item4</option>
<option value="5">Item5</option>
</select>

So Item 4 will show as "Selected" in the browser and now you want to change the value as 3 and show "Item3" as selected instead of Item4.So as per the above solutions,if you use

jQuery("#select_selector").val(3);

You will see that Item 3 as selected in browser.But when you process the data either in php or asp , you will find the selected value as "4".The reason is that , your html will look like this.

<select id="select_selector">
<option value="1">Item1</option>
<option value="2">Item2</option>
<option value="3" selected="selected">Item3</option>
<option value="4" selected="selected">Item4</option>
<option value="5">Item5</option>
</select>

and it gets the last value as "4" in sever side language.

SO MY FINAL SOLUTION ON THIS REGARD

newselectedIndex = 3;
jQuery("#select_selector option:selected").removeAttr("selected");
jQuery("#select_selector option[value='"+newselectedIndex +"']").attr('selected', 'selected');  

EDIT: Add single quote around "+newselectedIndex+" so that the same functionality can be used for non-numerical values.

So what I do is actually ,removed the selected attribute and then make the new one as selected.

I would appreciate comments on this from senior programmers like @strager , @y0mbo , @ISIK and others

After looking at some solutions, this worked for me.

I have one drop-down list with some values and I want to select the same value from another drop-down list... So first I put in a variable the selectIndex of my first drop-down.

var indiceDatos = $('#myidddl')[0].selectedIndex;

Then, I select that index on my second drop-down list.

$('#myidddl2')[0].selectedIndex = indiceDatos;

Note:

I guess this is the shortest, reliable, general and elegant solution.

Because in my case, I'm using selected option's data attribute instead of value attribute. So if you do not have unique value for each option, above method is the shortest and sweet!!

<asp:DropDownList ID="DropUserType" ClientIDMode="Static" runat="server">
     <asp:ListItem Value="1" Text="aaa"></asp:ListItem>
     <asp:ListItem Value="2" Text="bbb"></asp:ListItem>
</asp:DropDownList>

ClientIDMode="Static"

$('#DropUserType').val('1');

With hidden field you need to use like this:

$("._statusDDL").val(2);
$("._statusDDL").change();

or

$("._statusDDL").val(2).change();

I know this is a old question and the above solutions works fine except in some cases.

Like

<select id="select_selector">
<option value="1">Item1</option>
<option value="2">Item2</option>
<option value="3">Item3</option>
<option value="4" selected="selected">Item4</option>
<option value="5">Item5</option>
</select>

So Item 4 will show as "Selected" in the browser and now you want to change the value as 3 and show "Item3" as selected instead of Item4.So as per the above solutions,if you use

jQuery("#select_selector").val(3);

You will see that Item 3 as selected in browser.But when you process the data either in php or asp , you will find the selected value as "4".The reason is that , your html will look like this.

<select id="select_selector">
<option value="1">Item1</option>
<option value="2">Item2</option>
<option value="3" selected="selected">Item3</option>
<option value="4" selected="selected">Item4</option>
<option value="5">Item5</option>
</select>

and it gets the last value as "4" in sever side language.

SO MY FINAL SOLUTION ON THIS REGARD

newselectedIndex = 3;
jQuery("#select_selector option:selected").removeAttr("selected");
jQuery("#select_selector option[value='"+newselectedIndex +"']").attr('selected', 'selected');  

EDIT: Add single quote around "+newselectedIndex+" so that the same functionality can be used for non-numerical values.

So what I do is actually ,removed the selected attribute and then make the new one as selected.

I would appreciate comments on this from senior programmers like @strager , @y0mbo , @ISIK and others

<asp:DropDownList id="MyDropDown" runat="server" />

Use $("select[name$='MyDropDown']").val().

Just a note - I've been using wildcard selectors in jQuery to grab items that are obfuscated by ASP.NET Client IDs - this might help you too:

<asp:DropDownList id="MyDropDown" runat="server" />

$("[id* = 'MyDropDown']").append("<option value='-1'>&nbsp;</option>"); //etc

Note the id* wildcard- this will find your element even if the name is "ctl00$ctl00$ContentPlaceHolder1$ContentPlaceHolder1$MyDropDown"

Pure JS

For modern browsers using CSS selectors is not a problem for pure JS

document.querySelector('._statusDDL').value = 2;

function change() {
  document.querySelector('._statusDDL').value = 2;
}

<select class="_statusDDL">
  <option value="1" selected>A</option>
  <option value="2">B</option>
  <option value="3">C</option>
</select>

<button onclick="change()">Change</button>

If we have a dropdown with a title of "Data Classification":

<select title="Data Classification">
    <option value="Top Secret">Top Secret</option>
    <option value="Secret">Secret</option>
    <option value="Confidential">Confidential</option>
</select>

We can get it into a variable:

var dataClsField = $('select[title="Data Classification"]');

Then put into another variable the value we want the dropdown to have:

var myValue = "Top Secret";  // this would have been "2" in your example

Then we can use the field we put into dataClsField, do a find for myValue and make it selected using .prop():

dataClsField.find('option[value="'+ myValue +'"]').prop('selected', 'selected');

Or, you could just use .val(), but your selector of . can only be used if it matches a class on the dropdown, and you should use quotes on the value inside the parenthesis, or just use the variable we set earlier:

dataClsField.val(myValue);

How are you loading the values into the drop down list or determining which value to select? If you are doing this using Ajax, then the reason you need the delay before the selection occurs could be because the values were not loaded in at the time that the line in question executed. This would also explain why it worked when you put an alert statement on the line before setting the status since the alert action would give enough of a delay for the data to load.

If you are using one of jQuery's Ajax methods, you can specify a callback function and then put $("._statusDDL").val(2); into your callback function.

This would be a more reliable way of handling the issue since you could be sure that the method executed when the data was ready, even if it took longer than 300 ms.

So I changed it so that now it executes after a 300 miliseconds using setTimeout. Seems to be working now.

I have run into this many times when loading data from an Ajax call. I too use .NET, and it takes time to get adjusted to the clientId when using the jQuery selector. To correct the problem that you're having and to avoid having to add a setTimeout property, you can simply put "async: false" in the Ajax call, and it will give the DOM enough time to have the objects back that you are adding to the select. A small sample below:

$.ajax({
    type: "POST",
    url: document.URL + '/PageList',
    data: "{}",
    async: false,
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function (response) {
        var pages = (typeof response.d) == 'string' ? eval('(' + response.d + ')') : response.d;

        $('#locPage' + locId).find('option').remove();

        $.each(pages, function () {
            $('#locPage' + locId).append(
                $('<option></option>').val(this.PageId).html(this.Name)
            );
        });
    }
});

Another option is to set the control param ClientID="Static" in .net and then you can access the object in JQuery by the ID you set.

In my case I was able to get it working using the .attr() method.

$("._statusDDL").attr("selected", "");

How are you loading the values into the drop down list or determining which value to select? If you are doing this using Ajax, then the reason you need the delay before the selection occurs could be because the values were not loaded in at the time that the line in question executed. This would also explain why it worked when you put an alert statement on the line before setting the status since the alert action would give enough of a delay for the data to load.

If you are using one of jQuery's Ajax methods, you can specify a callback function and then put $("._statusDDL").val(2); into your callback function.

This would be a more reliable way of handling the issue since you could be sure that the method executed when the data was ready, even if it took longer than 300 ms.

<asp:DropDownList id="MyDropDown" runat="server" />

Use $("select[name$='MyDropDown']").val().

These solutions seem to assume that each item in your drop down lists has a val() value relating to their position in the drop down list.

Things are a little more complicated if this isn't the case.

To read the selected index of a drop down list, you would use this:

$("#dropDownList").prop("selectedIndex");

To set the selected index of a drop down list, you would use this:

$("#dropDownList").prop("selectedIndex", 1);

Note that the prop() feature requires JQuery v1.6 or later.

Let's see how you would use these two functions.

Supposing you had a drop down list of month names.

<select id="listOfMonths">
  <option id="JAN">January</option>
  <option id="FEB">February</option>
  <option id="MAR">March</option>
</select>

You could add a "Previous Month" and "Next Month" button, which looks at the currently selected drop down list item, and changes it to the previous/next month:

<button id="btnPrevMonth" title="Prev" onclick="btnPrevMonth_Click();return false;" />
<button id="btnNextMonth" title="Next" onclick="btnNextMonth_Click();return false;" />

And here's the JavaScript which these buttons would run:

function btnPrevMonth_Click() {
    var selectedIndex = $("#listOfMonths").prop("selectedIndex");
    if (selectedIndex > 0) {
        $("#listOfMonths").prop("selectedIndex", selectedIndex - 1);
    }
}
function btnNextMonth_Click() {
    //  Note:  the JQuery "prop" function requires JQuery v1.6 or later
    var selectedIndex = $("#listOfMonths").prop("selectedIndex");
    var itemsInDropDownList = $("#listOfMonths option").length;

    //  If we're not already selecting the last item in the drop down list, then increment the SelectedIndex
    if (selectedIndex < (itemsInDropDownList - 1)) {
        $("#listOfMonths").prop("selectedIndex", selectedIndex + 1);
    }
}

My site is also useful for showing how to populate a drop down list with JSON data:

http://mikesknowledgebase.com/pages/Services/WebServices-Page8.htm

Just try with

$("._statusDDL").val("2");

and not with

$("._statusDDL").val(2);

If we have a dropdown with a title of "Data Classification":

<select title="Data Classification">
    <option value="Top Secret">Top Secret</option>
    <option value="Secret">Secret</option>
    <option value="Confidential">Confidential</option>
</select>

We can get it into a variable:

var dataClsField = $('select[title="Data Classification"]');

Then put into another variable the value we want the dropdown to have:

var myValue = "Top Secret";  // this would have been "2" in your example

Then we can use the field we put into dataClsField, do a find for myValue and make it selected using .prop():

dataClsField.find('option[value="'+ myValue +'"]').prop('selected', 'selected');

Or, you could just use .val(), but your selector of . can only be used if it matches a class on the dropdown, and you should use quotes on the value inside the parenthesis, or just use the variable we set earlier:

dataClsField.val(myValue);

I use an extend function to get client ids, like so:

$.extend({
    clientID: function(id) {
        return $("[id$='" + id + "']");
    }
});

Then you can call ASP.NET controls in jQuery like this:

$.clientID("_statusDDL")

How are you loading the values into the drop down list or determining which value to select? If you are doing this using Ajax, then the reason you need the delay before the selection occurs could be because the values were not loaded in at the time that the line in question executed. This would also explain why it worked when you put an alert statement on the line before setting the status since the alert action would give enough of a delay for the data to load.

If you are using one of jQuery's Ajax methods, you can specify a callback function and then put $("._statusDDL").val(2); into your callback function.

This would be a more reliable way of handling the issue since you could be sure that the method executed when the data was ready, even if it took longer than 300 ms.

With hidden field you need to use like this:

$("._statusDDL").val(2);
$("._statusDDL").change();

or

$("._statusDDL").val(2).change();

Just try with

$("._statusDDL").val("2");

and not with

$("._statusDDL").val(2);

So I changed it so that now it executes after a 300 miliseconds using setTimeout. Seems to be working now.

I have run into this many times when loading data from an Ajax call. I too use .NET, and it takes time to get adjusted to the clientId when using the jQuery selector. To correct the problem that you're having and to avoid having to add a setTimeout property, you can simply put "async: false" in the Ajax call, and it will give the DOM enough time to have the objects back that you are adding to the select. A small sample below:

$.ajax({
    type: "POST",
    url: document.URL + '/PageList',
    data: "{}",
    async: false,
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function (response) {
        var pages = (typeof response.d) == 'string' ? eval('(' + response.d + ')') : response.d;

        $('#locPage' + locId).find('option').remove();

        $.each(pages, function () {
            $('#locPage' + locId).append(
                $('<option></option>').val(this.PageId).html(this.Name)
            );
        });
    }
});

Just an FYI, you don't need to use CSS classes to accomplish this.

You can write the following line of code to get the correct control name on the client:

$("#<%= statusDDL.ClientID %>").val("2");

ASP.NET will render the control ID correctly inside the jQuery.

Pure JS

For modern browsers using CSS selectors is not a problem for pure JS

document.querySelector('._statusDDL').value = 2;

function change() {
  document.querySelector('._statusDDL').value = 2;
}

<select class="_statusDDL">
  <option value="1" selected>A</option>
  <option value="2">B</option>
  <option value="3">C</option>
</select>

<button onclick="change()">Change</button>

How are you loading the values into the drop down list or determining which value to select? If you are doing this using Ajax, then the reason you need the delay before the selection occurs could be because the values were not loaded in at the time that the line in question executed. This would also explain why it worked when you put an alert statement on the line before setting the status since the alert action would give enough of a delay for the data to load.

If you are using one of jQuery's Ajax methods, you can specify a callback function and then put $("._statusDDL").val(2); into your callback function.

This would be a more reliable way of handling the issue since you could be sure that the method executed when the data was ready, even if it took longer than 300 ms.

Just an FYI, you don't need to use CSS classes to accomplish this.

You can write the following line of code to get the correct control name on the client:

$("#<%= statusDDL.ClientID %>").val("2");

ASP.NET will render the control ID correctly inside the jQuery.

Just try with

$("._statusDDL").val("2");

and not with

$("._statusDDL").val(2);