AngularJS动态生成select下拉框的方法实例

日期：2020-07-17 栏目：前端经验浏览：次

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。

转载注明出处：http://www.duanlonglong.com/qdjy/660.html

AngularJS动态生成select下拉框的方法实例

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