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Setting a value in a dropdown question with JavaScript

hahnimk
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6 years 4 months ago - 6 years 4 months ago #198464 by hahnimk

Setting a value in a dropdown question with JavaScript was created by hahnimk

Dear LimeSurvey community,

I am trying to set the value of a dropdown question with JavaScript.

After searching this forum, I found a function that sets the first non-empty value of the dropdown question, if no value is selected:

Code:

<script type="text/javascript" charset="utf-8">
 
	$(document).ready(function(){
 
		$('#questionQQ select').each(function(i) {
			if($(this).val() == '') {
				$('option[value!=""]:first', this).attr('selected', 'selected');
			}
		});
	});
 
</script>

Unfortunately, I don't know how to adapt this code to fit my needs. In my case, I am requesting the value for the dropdown selection with an HTTP request. Afterwards, I simply want to set the value to one of "A1", "A2", "A3", or "A4" (see attached screenshot). My current approach doesn't effect the selected value:

Code:

<script type="text/javascript" charset="utf-8">
// Once document is loaded
$(document).ready(function () {

    // HTTP request to get chat bot parameters
    let httpReq = new XMLHttpRequest();
    httpReq.open("GET", "www.URL.com", true);
    httpReq.send();
    httpReq.onreadystatechange = function () {
        if (httpReq.readyState === 4 && httpReq.status === 200) {
            const response = httpReq.responseText;
            const obj = JSON.parse(response);
            console.log(obj);
            
            const dropDownSelection = "A" + obj.experimentGroup;

            $('#question30059 select').each(function(i) {
                if($(this).val() == "") {
                    $('option[value==' + dropDownSelection + ']', this).attr('selected', 'selected');
                }
            });
            
        }
    };
});
</script>

I am looking forward to your responses!

Thanks in advance

...LimeSurvey.png

Last edit: 6 years 4 months ago by hahnimk.

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Joffm
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6 years 4 months ago #198470 by Joffm

Replied by Joffm on topic Setting a value in a dropdown question with JavaScript

Hi,

first non-empty value of the dropdown question, if no value is selected

What is the "first non-empty value"?

And is it correct that you want to set this value afterwards, if the respondent didn't select anything?

I see in your second script that you want to set the value to "obj.experimentGroup".
How do you get this value?
Is it some kind of a least filled approach? This you can do by an ajax call and ExpressionScript.

So, I'd really appreciate if you explained the design a bit better.

Joffm

BTW: The script you found somewhere is a real old one.
The "QQ" in "#questionQQ" indicates that the question code has to be inserted, like "#question1234".
Nowadays the {QID} is used for that.

Volunteers are not paid.
Not because they are worthless, but because they are priceless

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hahnimk
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6 years 4 months ago - 6 years 4 months ago #198471 by hahnimk

Replied by hahnimk on topic Setting a value in a dropdown question with JavaScript

Hi Joffm,

Thanks for your answer!

You are right, the first script is pretty old (7 years). I got it from the following post from tpartner, where the goal was to set a default value for the dropdown: www.limesurvey.org/de/foren/can-i-do-thi...er-in-dropdown-array .

By the "first non-empty value" I am referring to tpartner's post, where he said that "the first option that has a value is selected". I guess the following code snippet corresponds to this:

Code:

$('option[value!=""]:first', this).attr('selected', 'selected');

In my case, I set up an online experiment, in which participants get invited via email containing a unique user id. Based on this user id, I want to set the pre-determined experiment group (and other variables). So what I did was to set up a server under " www.URL.com " which has an HTTP endpoint that takes the user id as an argument and sends the experiment group back. The experiment group is a number between 1 and 4. The entire workflow is described as follows:

Participant receives user id per email
Participant enters user id in LimeSurvey field
User id is sent via HTTP request to server and experiment group (and other variables) are returned as a response (this is how I get "obj.experimentGroup")
The experiment group (and other variables) are saved in hidden fields of the survey
Based on the experiment group, the participants will see different versions of the survey

I was already able to save the other variables, e.g. the price path, to hidden text fields using this:

Code:

$('#question{30055} input[type="text"]').val([obj.pricePath]);

However, I don't know how to do the corresponding for a dropdown question.

I hope the above clarifies my question.

Thanks a lot

Last edit: 6 years 4 months ago by hahnimk.

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tpartner
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6 years 4 months ago #198475 by tpartner

Replied by tpartner on topic Setting a value in a dropdown question with JavaScript

However, I don't know how to do the corresponding for a dropdown question.

Code:

$('#question{QID} select').val(yourVariable);

Cheers,
Tony Partner
Solutions, code and workarounds presented in these forums are given without any warranty, implied or otherwise.

The following user(s) said Thank You: hahnimk

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hahnimk
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6 years 4 months ago #198476 by hahnimk

Replied by hahnimk on topic Setting a value in a dropdown question with JavaScript

Hi tpartner,

Wow, that was easy :laugh:
Works perfectly, thanks a lot!

Can you recommend a documentation to me, where I can get this kind of information from? E.g. how to deal with different question types with JavaScript.

Thanks

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