Populating dropdown menu with JSON Data

问题:

I'm tyring to use AJAX to populate a dropdown box based on the selection of another dropdown. I followed a tutorial using jQuery located here - http://remysharp.com/2007/01/20/auto-populating-select-boxes-using-jquery-ajax/ and have altered the select box ID names in the select box names in the script.

When there's a change to the value of the main checkbox the ajax is sent and returns as below:

{"1":"Kieran Hutchinson","2":"Caleb Tan","3":""}

THis is slightly different to the JSON string that is returned in the tutorials code which looks like this

[{optionValue:10, optionDisplay: 'Remy'}, {optionValue:11, optionDisplay: 'Arif'}, {optionValue:12, optionDisplay: 'JC'}]

I'm thinking this is the issue but I have no idea how to get the correct values out of my JSON response.

The javascript is as below:

$(function(){
            $("select#ContactCompanyId").change(function(){
              $.getJSON("contactList",{id: $(this).val(), ajax: 'true'}, function(j){
                var options = '';
                for (var i = 0; i < j.length; i++) {
                  options += '<option value="' + j[i].optionValue + '">' + j[i].optionDisplay + '</option>';
            }
                $("select#QuoteContactId").html(options);
                })
            })
        })  

Thanks in advance

回答1:

Your problem is this line:

options += '<option value="' + j[i].optionValue + '">' + j[i].optionDisplay + '</option>';

is expecting data sent in the format of the tutorial. Yours is a different format. Try:

options += '<option value="' + i + '">' + j[i] + '</option>';

You have the 'value' as just an index -- i, and the value as the value with that key, j[i]. so the option tag you'd end up with would look like this:

<option value="1">Kieran Hutchinson</option>

To explain more: the original data was in format like this:

// The tutorial data
array[0]['optionValue'] = 10;
array[0]['optionDisplay'] = 'Remy';

// Your data
array[1] = 'Kieran Hutchinson';

also, if that was actual data returned in your example, your iterator for (var i = 0; i < j.length; i++) will fail because you aren't starting at an index of 0. Use for(i in j) { ... }

回答2:

Since JSON can be considered as associative array also, you may do smth like this:

$(function(){
        $("select#ContactCompanyId").change(function(){
          $.getJSON("contactList",{id: $(this).val(), ajax: 'true'}, function(j){
            var options = '';
            for (key in j) {
                options += '<option value="' + key + '">' + j[key]+ '</option>';
            }
            $("select#QuoteContactId").html(options);
            })
        })
})  

More info about JSON can be found in this article - "Mastering JSON"

回答3:

If an array does not start with a 0 index, it is converted into a JSON Object with keys and values instead of an Array. Just use $.each to loop through, grabbing the key (i.e. 1) and the value (i.e. Kieran Hutchinson):

$(function(){
  $("select#ContactCompanyId").change(function(){
    $.getJSON("contactList",{id: $(this).val(), ajax: 'true'}, function(j){
      var options = '';
      $.each(j, function(key, value){
        options += '<option value="' + key + '">' + value + '</option>';
      })
      $("select#QuoteContactId").html(options);
    })
  })
})  

回答4:

If you could slightly change your response to return value and text keys in JSON:

[{value:10, text: 'Remy'}, {value:11, text: 'Arif'}, {value:12, text: 'JC'}]

you could use JQuery view engine and just load the array into a dropdown:

 $.getJSON("contactList",
           {id: $(this).val(), ajax: 'true'},
           function(j){
                $("select#QuoteContactId").view(response);
           })

See details here: https://jocapc.github.io/jquery-view-engine/docs/ajax-dropdown