Tips for Successfully Capturing Form Data with OnChange Event

On my website, I have set up a dedicated page for testing the functions I have developed, totaling around 30 to 40 so far. I have implemented a drop-down menu to list out these functions by name. When a function is selected, I trigger it using onChange with "window.location" and a Select Case structure. I pass the index through the query string using this.selectedIndex in the onChange event. This method was working perfectly until I realized I also needed to capture the value of the selected option (the name of the function being tested), not just the index value. However, I discovered that window.location does not send form values back, rendering them unavailable. I tried using "location.reload" to post back the data, but that did not solve the issue.

After some research, I attempted to pass the option value data via the query string by using "this.selectedOptions", but unfortunately, that did not work either. I have included a snippet of the code below, which functions correctly, but I am unable to retrieve the text value of the selected option.

<form action="testcodepage.asp" method="post">
  <select class="rounded " name="cboSearchCategories "
     onChange='window.location="<%=sRootDomain%>/testcode/template/testcodepage.asp?TestCategory=" + this.selectedIndex;'

    <option value="Select One">Select One</option>
    <option value="SearchEquipmentDB()">SearchEquipmentDB()-Case #1</option>
    <option value="DisplaySingleItem()">DisplaySingleItem()-Case #2</option>
    <option value="CreateJSONSchema()">CreateJSONSchema()-Case #3</option>
    <option value="UnlockChilkatAPI()">UnlockChilkatAPI()-Case #4</option>
  </select>
</form>

If there is a way to make this work without using a submit button, I would greatly appreciate any help! It's worth noting that this code is written in ASP Classic, but the solution would be relevant for any form submission method.

Answer №1

After exploring different solutions for the onchange event, I found a way to not only submit the form but also retrieve the index value. While the initial suggestion worked well, it lacked the ability to access all POST data. Below is the code that addresses this issue. It's worth noting that the first solution, recommended by @James, also functions but may not be as practical in certain scenarios.

Dim aDropDownValue
Dim sTestSearchCategory
Dim iCboIndex: iCboIndex = 0

<form action="testcodepage.asp" method="post">
  <select class="rounded" name="cboSearchCategories" id="cboSearchCategories" onchange="this.form.submit()">
    <option value="Select One|0" <%=IfSelected(sSearchCategory, "Select One")%>>Select One</option>
    <option value="SearchEquipmentDB()|1" <%=IfSelected(sSearchCategory, "SearchEquipmentDB()")%>>SearchEquipmentDB()-Case #1</option>
    <option value="DisplaySingleItem()|2" <%=IfSelected(sSearchCategory, "DisplaySingleItem()")%>>DisplaySingleItem()-Case #2</option>
  </select>
</form>

sTestSearchCategory = Trim(Request.Form("cboSearchCategories"))
If sTestSearchCategory <> "" Then
   aDropDownValue = Split(sTestSearchCategory, "|")
   sTestSearchCategory = aDropDownValue(0)
   iCboIndex = aDropDownValue(1)
End If

Select Case iCboIndex
  Case 1 ' Test the SearchEquipmentDB() function.
     Response.Write("Now testing the ") & sTestSearchCategory & " function." & "<br>"
  Response.End

  Case 2 ' Test the DisplaySingleItem() function.
     Response.Write("Now testing the ") & sTestSearchCategory & " function." & "<br>"
  Response.End

  Case Else
  Response.End

End Select          

Answer №2

In order to capture changes in a form field, you can utilize the addEventListener method and listen for the change event. By accessing e.target, you can retrieve the modified form field and its corresponding value using e.target.value.

<form name="UpdatedForm" action="" method="post">
  <b>Choose a Category:</b>&nbsp;
  <select class="rounded" name="category" id="category">
    <option value="Select Option">Select Option</option>
    <option value="Option1()">Option1()-Case #1</option>
    <option value="Option2()">Option2()-Case #2</option>
    <option value="Option3()">Option3()-Case #3</option>
    <option value="Option4()">Option4()-Case #4</option>
  </select>
</form>
<script>
  document.forms.UpdatedForm.addEventListener('change', e => {
    window.location = "/updatedcode/template/updatedpage.asp?Category="
      + e.target.value;
  });
</script>

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