javascript - charAt 返回为未定义

Question

我有以下函数，但它说 charAt 未定义。该错误与警报行有关。如果我执行 alert(value) 它给我的值没有问题。

$scope.markAnswer = function(answerID, questionID) {
        if ($scope.containsObject(answerID, $scope.selectedAnswer)) {
            $scope.selectedAnswer.splice($scope.selectedAnswer.indexOf(answerID), 1);
        } else {
            $scope.selectedAnswer.push(answerID);
        }

        angular.forEach($scope.selectedAnswer, function(value, key) {
            alert(value.charAt(0));
            if(questionID == res){
                $log.info("questionID");
            }

        });
    }

以下错误:

 TypeError: undefined is not a function
    at http://127.0.0.1:9000/modules/core/controllers/home.js:57:25
    at Object.forEach (http://127.0.0.1:9000/lib/angular/angular.js:325:18)
    at Scope.$scope.markAnswer (http://127.0.0.1:9000/modules/core/controllers/home.js:56:17)
    at http://127.0.0.1:9000/lib/angular/angular.js:10903:21
    at http://127.0.0.1:9000/lib/angular-touch/angular-touch.js:441:9
    at Scope.$eval (http://127.0.0.1:9000/lib/angular/angular.js:12811:28)
    at Scope.$apply (http://127.0.0.1:9000/lib/angular/angular.js:12909:23)
    at HTMLDivElement.<anonymous> (http://127.0.0.1:9000/lib/angular-touch/angular-touch.js:440:13)
    at HTMLDivElement.jQuery.event.dispatch (http://127.0.0.1:9000/lib/jquery/dist/jquery.js:4430:9)
    at HTMLDivElement.elemData.handle (http://127.0.0.1:9000/lib/jquery/dist/jquery.js:4116:28)

Answer 1

你可以试试这个:

String(value).charAt(0)

我想这是因为您的值不是字符串，而 charAt 是一种返回 string 中指定索引处字符的方法。