用户从下拉列表框中选择选项后，如何获取新选择的值和旧的值? [英] How to get new selected and old values after user selected option from dropdown list box?

问题描述

我有angularjs下拉列表框:

I have angularjs dropdown list box:

    <select class="form-control"
            ng-model="editor.frequency"
            ng-options="item as item.Name for item in editor.frequencies"
            ng-change="editor.editFrequencyManual = false;">
   </select>

在用户单击下拉列表框中的选项后，我需要获取被单击(选定)的值和旧值(在选定之前).

After user click on option in dropdown list box I need to get clicked(selected) value and the old value(before selection).

任何想法我怎么能得到这两个值?我应该使用事件函数吗?

Any idea how can I get this two values?Is there event function that I sholud use?

推荐答案

您可以查看模型上的更改:

You could watch the changes on your model:

$scope.$watch('editor', function(newValue, oldValue){
    //
});

或者您可以修改 ng-change ，以使其将新旧值作为参数传递:

Or you could modify ng-change so that it passes old and new values as parameters:

    <select class="form-control"
            ng-model="editor.frequency"
            ng-options="item as item.Name for item in editor.frequencies"
            ng-change="changed(editor.frequency, {{editor.frequency}}); editor.editFrequencyManual = false;">
   </select>

当然，您应该将 editor.editFrequencyManual = false; 移到更改函数中.

Of course, you should move editor.editFrequencyManual = false; into the change function.

function myController($scope) {
  $scope.myModel = {};
  $scope.doThis = function(newValue, oldValue) {
    console.log("New value: " + newValue);
    console.log("Old value: " + oldValue);
  }
}

angular.module('myApp', []);
angular
  .module('myApp')
  .controller('myController', myController);

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.5.6/angular.min.js"></script>
<div ng-app="myApp">
  <div ng-controller="myController">
      <select ng-model="myModel" ng-change="doThis(myModel, '{{myModel}}');">
        <option value="1">1</option>
        <option value="2">2</option>
        <option value="3">3</option>
      </select>
    </div>
</div>

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