javascript - ng-repeat 只添加一次

Question

使用 AngularJS 有一种方法可以只添加一次项目。对于下面的这段代码，假设我输入 F 并将其添加到项目列表中。有没有办法限制我或任何用户再次添加 F ？

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="myApp">
    <div ng-controller="MyCtrl">
        <ul>
            <li ng-repeat="item in items track by $index">{{item}}</li>
        </ul>
        <input ng-model="newItem" type="text"></input>
        <button ng-click="add(newItem)">Add</button>
    </div>
</div>

<script>
var app = angular.module('myApp', []);

app.controller('MyCtrl', function($scope) {
    $scope.items = ["A", "B", "C", "D"];
    $scope.add = function(item) {
        $scope.items.push(item);
    };

});
</script>

Answer 1

ES5

您必须在您的方法中手动检查它。

$scope.add = function (item) {
    if ($scope.items.indexOf(item) === -1) {
        $scope.items.push(item);
    }
};

---

ES6

您可以使用 Set .

The Set object lets you store unique values of any type

$scope.items = new Set(["A", "B", "C", "D"]);

$scope.add = function (item) {
    $scope.items.add(item);
};