AngularJS之动态生成select下拉框

时间:2019-09-22
本文章向大家介绍AngularJS之动态生成select下拉框，主要包括AngularJS之动态生成select下拉框使用实例、应用技巧、基本知识点总结和需要注意事项，具有一定的参考价值，需要的朋友可以参考一下。

一、select相关知识

<select>
    <option value="0">HTML</option>
    <option value="1">Java</option>
    <option value="2">Python</option>
</select>

其中，value 是存储到数据库的值，在此处为0，1，2这些数值，label 为显示在页面的值，在此处为Html、Java这些字符。

二、ng-options

1.数组作为数据源

  • label for value in array
  • select as label for value in array
  • label group by group for value in array

代码1(数组中为字符串)

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://cdn.staticfile.org/angular.js/1.4.6/angular.min.js"></script>
</head>
<body>

<div ng-app="myApp" ng-controller="myCtrl">
    <!--
        这里的label和value需一致，否则会报错
        表达式语法：label for value in array
    -->
    <select ng-model="name" ng-options="name for name in names"></select>
</div>

<script>
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.names = ['baidu', 'Google', 'apple'];
});
</script>
</body>
</html>

最终得到的结果为：

<select ng-model="name" ng-options="name for name in names" class="ng-pristine ng-valid ng-touched">
    <option value="?" selected="selected"></option>
    <option value="string:baidu" label="baidu">baidu</option>
    <option value="string:Google" label="Google">Google</option>
    <option value="string:apple" label="apple">apple</option>
</select>

需要注意的是，在最后生成的html代码中option的value 值为String:baidu ，会在数组中原有的字符串之前加上其类型的标识，这个通过百度了解到是因为angularjs版本问题造成，具体未测试。

代码2（数组中为一个对象）

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://cdn.staticfile.org/angular.js/1.4.6/angular.min.js"></script>
</head>
<body>
<div ng-app="myApp" ng-controller="myCtrl">
    <!--
        表达式语法：label for value in array
    -->
    <select ng-model="name" ng-options="c.id for c in coms"></select>
</div>
<script>
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.coms = [
        {'id':'baidu','name':'百度'}, 
        {'id':'Google', 'name':'谷歌'}, 
        {'id':'apple', 'name':'苹果'}];
});
</script>
</body>
</html>

最终得到的html代码为：

<!-- 注意：此处ng-model绑定的name变量并非选中项的name属性，而是选中项的全部属性
    如选中了索引为0项，则name={"id":"baidu","name":"百度"}
    这边ng-model绑定变量为值为select的value值
-->
<select ng-model="name" ng-options="c.id for c in coms" class="ng-pristine ng-valid ng-touched">
    <option value="?" selected="selected"></option>
    <option value="object:3" label="baidu">baidu</option>
    <option value="object:4" label="Google">Google</option>
    <option value="object:5" label="apple">apple</option>
</select>

通过生成的html代码，我们可以看到这样写会使得最终的option 的value 值显示为数据类型，而实际想要得到的结果是显示我们选中的值，因此需要写为：

<!--
    表达式语法:select as label for value in array
        c.id作为select的value，c.name作为select的label
-->
ng-options="c.id as c.name for c in coms"

其中，c.id 对应value ，c.name 对应label 。生成html代码为：

<select ng-model="name" ng-options="c.id as c.name for c in coms" class="ng-pristine ng-valid ng-touched">
    <option value="?" selected="selected"></option>
    <option value="string:baidu" label="百度">百度</option>
    <option value="string:Google" label="谷歌">谷歌</option>
    <option value="string:apple" label="苹果">苹果</option>
</select>

代码3（根据对象属性分类）

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://cdn.staticfile.org/angular.js/1.4.6/angular.min.js"></script>
</head>
<body>

<div ng-app="myApp" ng-controller="myCtrl">
    <!--
        表达式语法：label group by group for value in array
    -->
    <select ng-options="c.name group by c.type for c in coms" ng-model="name" ></select>
</div>

<script>
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.coms = [{'id':'baidu','name':'百度','type':'搜索'}, 
                   {'id':'Google', 'name':'谷歌','type':'搜索'}, 
                   {'id':'apple', 'name':'苹果','type':'手机'},
                   {'id':'TaoBao', 'name':'淘宝','type':'购物'}
                ];
});
</script>
</body>
</html>

得到的html代码为：

<select ng-options="c.name group by c.type for c in coms" ng-model="name" class="ng-pristine ng-valid ng-touched">
    <optgroup label="搜索">
        <option value="object:3" label="百度" selected="selected">百度</option>
        <option value="object:4" label="谷歌">谷歌</option></optgroup>
    <optgroup label="手机">
        <option value="object:5" label="苹果">苹果</option>
    </optgroup>     
    <optgroup label="购物">
        <option value="object:6" label="淘宝">淘宝</option>
    </optgroup>
</select>

注意事项(默认选中问题)

通过以上最终得到的HTML代码可以发现，每次生成的代码都会默认选中一个空白的选项，如果需要手动指定一个默认选中值应该怎么设置？

我们有两种方式(此处代码不完整，验证时请将html部分补充完整)：

<!-- 以代码2中(label for value in array)和(select as label for value in array) 为例-->
<!-- 
    方式一:ng-init属性
    两种语法形式在使用ng-init时有一定区别，其中第二中写为了name=coms[0].id是因为在ng-options中通过     select as 为当前的select指定了coms[0].id作为value的值；在写法一种未指定value值，则默认为coms中    的一个对象。
-->
<select ng-init="name1=coms[0]" ng-options="c.name for c in coms" ng-model="name1"></select>
<select ng-init="name2=coms[0].id" ng-options="c.id as c.name for c in coms" ng-model="name2"></select>

<!--
    方式二： 在js代码中为ng-model绑定的变量赋值
-->
<script>
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.coms = [{'id':'baidu','name':'百度','type':'搜索'}, 
                   {'id':'Google', 'name':'谷歌','type':'搜索'}, 
                   {'id':'apple', 'name':'苹果','type':'手机'},
                   {'id':'TaoBao', 'name':'淘宝','type':'购物'}
                ];
    // label for value in array
    $scope.name1 = $scope.coms[0];
    
    // select as label for value in array
    $scope.name2 = $scope.coms[0].id;
});
</script>

2.对象作为数据源

  • label for (key, value) in object

代码展示

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://cdn.staticfile.org/angular.js/1.4.6/angular.min.js"></script>
</head>
<body>

<div ng-app="myApp" ng-controller="myCtrl">
    {{name4}}
    <!-- 
        表达式语法：select as label for (key, value) in object
    -->
    <select ng-options="value as key for (key, value) in province" ng-model='name4'></select>
</div>
<script>
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) { 
    $scope.province = {
        '北京':'京',
        '山西':'晋',
        '上海':'沪',
    };
});
</script>
</body>
</html>

3.全部语法

for array data sources:

  • label for value in array
  • select as label for value in array
  • label group by group for value in array
  • label disable when disable for value in array
  • label group by group for value in array track by trackexpr
  • label disable when disable for value in array track by trackexpr
  • label for value in array | orderBy:orderexpr track by trackexpr(for including a filter with track by)

for object data sources:

  • label for (key , value) in object
  • select as label for (key ,value) in object
  • label group by group for (key,value) in object
  • label disable when disable for (key, value) in object
  • select as label group by group for(key, value) in object
  • select as label disable when disable for (key, value) in object

三、ng-repeat

代码示例：

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://cdn.staticfile.org/angular.js/1.4.6/angular.min.js"></script>
</head>
<body>

<div ng-app="myApp" ng-controller="myCtrl">
    <select>
        <option value="" selected="selected">====请选择====</option>
        <option ng-repeat="com in coms" value="{{com.name}}">{{com.name}}</option>
    </select>
</div>

<script>
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.coms = [{'id':'baidu','name':'百度','type':'搜索'}, 
                   {'id':'Google', 'name':'谷歌','type':'搜索'}, 
                   {'id':'apple', 'name':'苹果','type':'手机'},
                   {'id':'TaoBao', 'name':'淘宝','type':'购物'}
                ];
});
</script>
</body>
</html>

四、总结

使用ng-repeat动态生成select比ng-option略微简单，但是ng-repeat有一定的局限性，选择的值只能是一个字符串，而使用ng-option选择的值可以是一个对象。

原文地址：https://www.cnblogs.com/otblog/p/11569291.html

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