Javascript charAt返回时未定义

我有下面的函数，但是它说字符是未定义的。错误与警戒线有关。如果我做了警报（值），它会给我的值没有问题

$scope.markAnswer = function(answerID, questionID) {
        if ($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");
            }

        });
    }

出现以下错误：

 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)

TypeError:未定义不是函数
在http://127.0.0.1:9000/modules/core/controllers/home.js:57:25
在Object.forEach(http://127.0.0.1:9000/lib/angular/angular.js:325:18)
在范围内。$Scope.markAnswer(http://127.0.0.1:9000/modules/core/controllers/home.js:56:17)
在http://127.0.0.1:9000/lib/angular/angular.js:10903:21
在http://127.0.0.1:9000/lib/angular-触摸/角度触摸。js:441:9
在范围内。$eval(http://127.0.0.1:9000/lib/angular/angular.js:12811:28)
在范围内。$apply(http://127.0.0.1:9000/lib/angular/angular.js:12909:23)
在HTMLDEVELENT。(http://127.0.0.1:9000/lib/angular-触摸/角度触摸。js:440:13）
在htmldevelment.jQuery.event.dispatch(http://127.0.0.1:9000/lib/jquery/dist/jquery.js:4430:9)
位于htmldevelment.elemData.handle(http://127.0.0.1:9000/lib/jquery/dist/jquery.js:4116:28)

您可以试试这个：

String(value).charAt(0)

---

我假设发生这种情况是因为您的值不是字符串，而

charAt

是一个返回字符串中指定索引处字符的方法。

值是字符串吗？请检查一下。谢谢，这很奇怪，因为即使在对字符串调用charAt（）时，它也会对其求值，但在控制台中它仍然会给出此错误。然而，这已经解决了它。