Why do I get a message saying forEach is not a function?

Question

In typescript I defined:

class SubjectService implements ISubjectService {

    subject: any;
    subjectId: number = 0;
    subjects = {
        "1": { "id": 1, "name": "Java" },
        "100": { "id": 100, "name": "Test" }
    };

    static $inject = [
        "$http",
        "appConstant",
    ];

    constructor(
        public $http: ng.IHttpService,
        public ac: IAppConstant
        ) {
    }

}

I then in my constructor have this code:

class SubjectController {

    static $inject = [
        "$scope",
        "subjectService"
    ];

    constructor(
        public $scope,
        public su: ISubjectService
        ) {
        $scope.su = su;

        $scope.rowClicked = (subject, $index) => {
            var self = this;
            if (subject.current && subject.current == true) {
                return;
            }
            su.subjects.forEach(function (subject) {
                subject.current = false;
            });
            su.subject = subject;
            su.subject.current = true;
        }

    }

}

But when this runs I am getting a message saying:

TypeError: su.subjects.forEach is not a function at Scope.SubjectController.$scope.rowClicked (http://localhost:1810/app/controllers/SubjectController.js:12:25)

Does anyone have any idea what might be wrong. I used similar code in other places but here it fails each time.

possible duplicate of [Why is "forEach not a function" for this map?](http://stackoverflow.com/questions/31096596/why-is-foreach-not-a-function-for-this-map) — Cerbrus, Jul 01 '15 at 13:35

score 3 · Accepted Answer · answered Jul 01 '15 at 13:32

3

subjects is an Object, not an Array, because of its {} notation. You can loop through 1 and 100 as keys if you like using Object.keys(subjects). You could also start it out as an empty array ([]) and then set the values of subjects[1] and subjects[100] if you like, but there's no shorthand inline way to just define two separated indices of an array without the inbetween ones.

answered Jul 01 '15 at 13:32

Katana314

8,429
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More details on the way to Object.keys(objName).forEach(...) - https://stackoverflow.com/questions/31096596/why-is-foreach-not-a-function-for-this-object/31096661 – BUDDHIKA Jun 25 '20 at 07:03

score 1 · Answer 2 · answered Jul 01 '15 at 13:31

1

su.subjects is an object, not an array and forEach is not defined for Object.

answered Jul 01 '15 at 13:31

phuzi

12,078
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score 1 · Answer 3 · answered Jul 01 '15 at 13:51

1

I would also note that forEach is not implemented in all versions of browsers (looking at you, IE 8) since forEach was not included until ECMA 5.1. See forEach

answered Jul 01 '15 at 13:51

Josh

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Why do I get a message saying forEach is not a function?

3 Answers3