如何用ng-switchh实现根据数组长度不同，显示不同的内容，假如用arr.length作为判断条件的话需要写很多情况，所以考虑用true作为判断条件，但是不知道ng-switch-when该怎么写，当然用ng-if也可以实现，只是对ng-switch的写法有疑问，谢谢。
代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>title</title>
<script src="angular.js"></script>
<style>
</style>
</head>
<body ng-app="App">
<div ng-controller="Ctrl">
<div ng-switch="arr.length">
<span ng-switch-when="1">1</span>
<span ng-switch-when="2">2</span>
<span ng-switch-when="3">3</span>
</div>
<div>
<span ng-if="arr.length<2">1---</span>
<span ng-if="arr.length>=2">2---</span>
</div>
<div ng-switch=true>
<span ng-switch-when="(arr.length==0)"> 1---true </span>
<span ng-switch-when="(arr.length==0)"> 2---true </span>
</div>
</div>
<script>
var App = angular.module("App", []);
App.controller("Ctrl", ["$scope", function ($scope) {
$scope.arr = [1, 2,3];
}]);
</script>
</body>
</html>
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