当使用 ng-repeat 构造选项时，从选择框中获取所有选项

Question

我正在尝试从下拉列表中检索所有选项。手动构建时我得到了所有选项，但使用 ng-repeat 构建时我无法获得它们。

var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.names = ["Emil", "Tobias", "Linus"];
    
     var x = document.getElementById("mySelect").options.length;
    document.getElementById("demo").innerHTML = "Found " + x + " options in the list.";
});

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angular.min.js"></script>
<div ng-app="myApp" ng-controller="myCtrl">
<p id="demo"></p>

<select id="mySelect" >
<option ng-repeat="x in names">{{x}}</option>
</select>


</div>

正如你在运行 sn -p 时看到的那样，找到的项目返回为“0”。

但如果您手动构建选项，则以下 sn-p 有效。

var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.names = ["Emil", "Tobias", "Linus"];
    
     var x = document.getElementById("mySelect").options.length;
    document.getElementById("demo").innerHTML = "Found " + x + " options in the list.";
});

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angular.min.js"></script>
<div ng-app="myApp" ng-controller="myCtrl">
<p id="demo"></p>

<select id="mySelect" >
<option >Emil</option>
<option >Tobias</option>
<option >Linus</option>
</select>


</div>

想知道当 ng-repeat 与 select 一起使用时如何获取所有选项。谢谢！

Answer 1

这是因为您的函数在 DOM 呈现之前执行。只需将您的代码包装在$timeout 中，它就会按预期工作，因为$timeout 只会在DOM 呈现后执行您的代码。

工作示例：

var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope, $timeout) {
    $scope.names = ["Emil", "Tobias", "Linus"];
    $timeout(function () {
        var x = document.getElementById("mySelect").options.length;
        document.getElementById("demo").innerHTML = "Found " + x + " options in the list.";
    });
    
});

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angular.min.js"></script>
<div ng-app="myApp" ng-controller="myCtrl">
<p id="demo"></p>

<select id="mySelect" >
<option ng-repeat="x in names">{{x}}</option>
</select>


</div>