選擇非空選項后默認選項消失

Question

我有我的問題JSFiddle 的簡單示例。

開始時我有空/默認選項，但是當我從下拉列表中選擇其他內容時，此選項消失。

選擇后如何離開此選項？

 <label for="mySelect">Make a choice:</label>
 <select name="mySelect" id="mySelect"
      ng-options="option.name for option in data.availableOptions"
      ng-model="data.selectedOption"></select>

角度控制器：

    .controller('ExampleController', ['$scope', function($scope) {
   $scope.data = {
    availableOptions: [
      {id: '1', name: 'Option A'},
      {id: '2', name: 'Option B'},
      {id: '3', name: 'Option C'}
    ],
    selectedOption: {id: '2', name: 'Option B'} //This sets the default value of the select in the ui
    };

我嘗試使用ng-init將默認選項設置為null但這不起作用

Answer 1

請在 select 元素中添加空的 option 元素並檢查。

 <select name="mySelect" id="mySelect"
  ng-options="option.name for option in data.availableOptions"
  ng-model="data.selectedOption">
    <option></option>
  </select>

Answer 2

使用這種方法：

HTML

<div ng-app="defaultValueSelect">
  <div ng-controller="ExampleController">
  <form name="myForm">
    <label for="mySelect">Make a choice:</label>
    <select name="mySelect" id="mySelect"
      ng-options="option.id as option.name for option in data.availableOptions"
      ng-model="data.selectedOption"></select>
  </form>
  <hr>
  <tt>option = {{data.selectedOption}}</tt><br/>
</div>

AngularJS

angular.module('defaultValueSelect', [])
 .controller('ExampleController', ['$scope', function($scope) {
   $scope.data = {
    availableOptions: [
      {id: '1', name: 'Option A'},
      {id: '2', name: 'Option B'},
      {id: '3', name: 'Option C'}
    ],
    selectedOption: '2' //This sets the default value of the select in the ui
    };

}]);