AngularJS - value attribute for select

问题

Source JSON data is:

[
  {"name":"Alabama","code":"AL"},
  {"name":"Alaska","code":"AK"},
  {"name":"American Samoa","code":"AS"},
  ...
]

I try

ng-options="i.code as i.name for i in regions"

but am getting:

<option value="?" selected="selected"></option>
<option value="0">Alabama</option>
<option value="1">Alaska</option>
<option value="2">American Samoa</option>

while I am expecting to get:

<option value="AL">Alabama</option>
<option value="AK">Alaska</option>
<option value="AS">American Samoa</option>

So, how to get value attributes and get rid of "?" item?

By the way, if I set the $scope.regions to a static JSON instead of AJAX request's result, the empty item disappears.

回答1:

What you first tried should work, but the HTML is not what we would expect. I added an option to handle the initial "no item selected" case:

<select ng-options="region.code as region.name for region in regions" ng-model="region">
   <option style="display:none" value="">select a region</option>
</select>
<br>selected: {{region}}

The above generates this HTML:

<select ng-options="..." ng-model="region" class="...">
   <option style="display:none" value class>select a region</option>
   <option value="0">Alabama</option>
   <option value="1">Alaska</option>
   <option value="2">American Samoa</option>
</select>

Fiddle

Even though Angular uses numeric integers for the value, the model (i.e., $scope.region) will be set to AL, AK, or AS, as desired. (The numeric value is used by Angular to lookup the correct array entry when an option is selected from the list.)

This may be confusing when first learning how Angular implements its "select" directive.

回答2:

You can't really do this unless you build them yourself in an ng-repeat.

<select ng-model="foo">
   <option ng-repeat="item in items" value="{{item.code}}">{{item.name}}</option>
</select>

BUT... it's probably not worth it. It's better to leave it function as designed and let Angular handle the inner workings. Angular uses the index this way so you can actually use an entire object as a value. So you can use a drop down binding to select a whole value rather than just a string, which is pretty awesome:

<select ng-model="foo" ng-options="item as item.name for item in items"></select>

{{foo | json}}

回答3:

If you use the track by option, the value attribute is correctly written, e.g.:

<div ng-init="a = [{label: 'one', value: 15}, {label: 'two', value: 20}]">
    <select ng-model="foo" ng-options="x for x in a track by x.value"/>
</div>

produces:

<select>
    <option value="" selected="selected"></option>
    <option value="15">one</option>
    <option value="20">two</option>
</select>

回答4:

If the model specified for the drop down does not exist then angular will generate an empty options element. So you will have to explicitly specify the model on the select like this:

<select ng-model="regions[index]" ng-options="....">

Refer to the following as it has been answered before:

Why does AngularJS include an empty option in select? and this fiddle

Update: Try this instead:

<select ng-model="regions[index].code" ng-options="i.code as i.name for i in regions">
</select>

or

<select ng-model="regions[2]" ng-options="r.name for r in regions">
</select>

Note that there is no empty options element in the select.

回答5:

You could modify you model to look like this:

$scope.options = {
    "AL" : "Alabama",
    "AK" : "Alaska",
    "AS" : "American Samoa"
  };

Then use

<select ng-options="k as v for (k,v) in options"></select>

回答6:

It appears it's not possible to actually use the "value" of a select in any meaningful way as a normal HTML form element and also hook it up to Angular in the approved way with ng-options. As a compromise, I ended up having to put a hidden input alongside my select and have it track the same model as my select, like this (all very much simplified from real production code for brevity):

HTML:

<select ng-model="profile" ng-options="o.id as o.name for o in profiles" name="something_i_dont_care_about">
</select>
<input name="profile_id" type="text" style="margin-left:-10000px;" ng-model="profile"/>

Javascript:

App.controller('ConnectCtrl',function ConnectCtrl($scope) {
$scope.profiles = [{id:'xyz', name:'a profile'},{id:'abc', name:'another profile'}];
$scope.profile = -1;
}

Then, in my server-side code I just looked for params[:profile_id] (this happened to be a Rails app, but the same principle applies anywhere). Because the hidden input tracks the same model as the select, they stay in sync automagically (no additional javascript necessary). This is the cool part of Angular. It almost makes up for what it does to the value attribute as a side effect.

Interestingly, I found this technique only worked with input tags that were not hidden (which is why I had to use the margin-left:-10000px; trick to move the input off the page). These two variations did not work:

<input name="profile_id" type="text" style="display:none;" ng-model="profile"/>

and

<input name="profile_id" type="hidden" ng-model="profile"/>

I feel like that must mean I'm missing something. It seems too weird for it to be a problem with Angular.

回答7:

you can use

state.name for state in states track by state.code

Where states in the JSON array, state is the variable name for each object in the array.

Hope this helps

回答8:

Try it as below:

var scope = $(this).scope();
alert(JSON.stringify(scope.model.options[$('#selOptions').val()].value));

来源：https://stackoverflow.com/questions/13803665/angularjs-value-attribute-for-select

标签

select

angularjs

options