从<input>值设置变量

Question

I need to implement Google Analytics (Universal/analytics.js) on a 20-something part AJAX-based questionnaire. The questionnaire works something like a choose-your-own-adventure, whereas the follow-up questions are all determined by the preceding answers.

Each input has a name and an ID. I'm interested in pulling the value from this field and setting it as a global variable in a dataLayer. Everything has a unique ID and Name, which I've started collecting in a database.

Here's an example of the HTML:

<table id="ctl00_ContentPlaceHolder1_2_Table1" class="CompSSRadio" cellpadding="1" cellspacing="1">
            <tr>
                <td class="CompSSRadioLabel">
                </td>
            </tr>
            <tr>
                <td class="CompSSRadioResponses">
                <table id="ctl00_ContentPlaceHolder1_2_1_48_1" class="CompSSRadioResponses" border="0">
                    <tr>
                        <td><input id="ctl00_ContentPlaceHolder1_2_1_48_1_0" type="radio" name="ctl00$ContentPlaceHolder1$2$1_48_1" value="4" /><label for="ctl00_ContentPlaceHolder1_2_1_48_1_0"><SPAN style="FONT-FAMILY: Museo 500"><SPAN style="FONT-SIZE: 14pt"><SPAN style="FONT-FAMILY: Museo 500"></SPAN>Test answer 1</SPAN></SPAN></label></td>
                    </tr><tr>
                        <td><input id="ctl00_ContentPlaceHolder1_2_1_48_1_1" type="radio" name="ctl00$ContentPlaceHolder1$2$1_48_1" value="5" /><label for="ctl00_ContentPlaceHolder1_2_1_48_1_1"><SPAN style="FONT-FAMILY: Museo 500"><SPAN style="FONT-SIZE: 14pt"><SPAN style="FONT-FAMILY: Museo 500"></SPAN>Test answer 2</SPAN></SPAN></label></td>
                    </tr>
                </table>
            </td>
            </tr>
        </table>

Here is the "next" button:

<input type="image" name="ctl00$ContentPlaceHolder1$btnNext2" id="ctl00_ContentPlaceHolder1_btnNext2" src="../App_Themes/Images/Right.gif" onclick="javascript: pageTracker._trackPageview('//forward.html');window.document.getElementById('ctl00_ContentPlaceHolder1_btnNext').disabled=true;window.document.getElementById('ctl00_ContentPlaceHolder1_btnNext2').disabled=true;__doPostBack('ctl00$ContentPlaceHolder1$btnNext2','');" style="border-width:0px;" />

And here is a script which does something with the form info:

<script type="text/javascript">
//<![CDATA[
var theForm = document.forms['aspnetForm'];
if (!theForm) {
    theForm = document.aspnetForm;
}
function __doPostBack(eventTarget, eventArgument) {
    if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
        theForm.__EVENTTARGET.value = eventTarget;
        theForm.__EVENTARGUMENT.value = eventArgument;
        theForm.submit();
    }
}
//]]>
</script>

I don't know if I need to hook into that or anything, since that's what's submitting information. Obviously I'm clueless. I feel like this is a fairly simple task, it's just my lack of javascript knowledge preventing me from crafting the necessary script.

Thanks ahead of time!

Answer 1

IF you are using radios to select one of multiple values, all radio elements must have the same name. For example, if you have:

<input type="radio" name="sex" value="Male" id="radio_male">
<label for="radio_male">Male</label>

<input type="radio" name="sex" value="Female" id="radio_female">
<label for="radio_female">Female</label>

You will only be able to select "Male" or "Female", but not both. Taking that in consideration, the way to access the selected value, in Javascript, should be:

var elements = document.getElementsByName("sex");

for (i = 0; i < elements.length; i++) {
    var el = elements[i];

    if ( el.checked ) {
        alert("Checked value: " + el.value);
        break; // Because only one radio from the group will be checked, there's no point in checking the rest of them, if there are more
    }
}

About Data Layer, I have no clue, but it sounds like you are having problems getting the values, if I'm understanding it well.