ng-options属性可以在表达式中使用数组或对象来自动生成一个select中的option列表。ng-options与ng-repeat很相似,很多时候可以用ng-repeat来代替ng-options。但是ng-options提供了一些好处,例如减少内存提高速度,以及提供选择框的选项来让用户选择。当select中一个选项被选择,该选项将会被绑定到ng-model。如果你想设一个默认值,可以像这样:$scope.selected = $scope.collection[3]。
之前一直在用ng-repeat就见到过track by,没有去了解它的用法,这次了解了一下。track by主要是防止值有重复,angularjs会报错。因为angularjs需要一个唯一值来与生成的dom绑定,以方便追踪数据。例如:items=[“a”,“a”,“b”],这样ng-repeat=“item in items”就会出错,而用ng-repeat=“(key,value) in items track by key”就不会出现错误了。
ng-options一般有以下用法:
对于数组:
- 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)
- 对于对象:
- 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
一个简单的例子:
Document
Select .
Currently selected: { { {selected_color:myColor} }}