Drilling down an object throws "Cannot read property of undefined" [REACT]

in the object below


throws name is undefined, or 0 is undefined
same as some nested obeject pls how do i resolve this…?

    "img": [
            "_id": "60a3eeef1af8e4244ce2b035",
            "name": "knots of love.jpg",
            "alternativeText": "",
            "caption": "",
            "hash": "knots_of_love_7814a03a3f",
            "ext": ".jpg",
            "mime": "image/jpeg",
            "size": 5.76,
            "width": 124,
            "height": 198,
            "url": "/uploads/knots_of_love_7814a03a3f.jpg",
            "formats": {
                "thumbnail": {
                    "name": "thumbnail_knots of love.jpg",
                    "hash": "thumbnail_knots_of_love_7814a03a3f",
                    "ext": ".jpg",
                    "mime": "image/jpeg",
                    "width": 98,
                    "height": 156,
                    "size": 4.18,
                    "path": null,
                    "url": "/uploads/thumbnail_knots_of_love_7814a03a3f.jpg"
            "provider": "local",
            "related": [
            "createdAt": "2021-05-18T16:44:31.322Z",
            "updatedAt": "2021-05-18T16:44:54.842Z",
            "__v": 0,
            "id": "60a3eeef1af8e4244ce2b035"
    "_id": "60a3ef061af8e4244ce2b036",
    "pageCount": 500,
    "title": "Knots of love",
    "description": "True Love knows no bound",
    "datePublished": "2019-11-01",
    "createdAt": "2021-05-18T16:44:54.832Z",
    "updatedAt": "2021-05-18T16:45:11.295Z",
    "__v": 0,
    "author": {
        "_id": "60a3e3591af8e4244ce2b031",
        "name": "Robert Gold",
        "createdAt": "2021-05-18T15:55:05.985Z",
        "updatedAt": "2021-05-18T15:55:05.997Z",
        "__v": 0,
        "id": "60a3e3591af8e4244ce2b031"
    "id": "60a3ef061af8e4244ce2b036"
1 Like

I know it’s rather an old question, but if anyone stumbles upon it, I want to share my case.

I got the same error just because I accessed data incorrectly. I fetched the endpoint based on a slug, with query param like this:

const post = await fetcher(`${process.env.NEXT_PUBLIC_HCMS_API_URL}/posts?slug=${params.slug}`)

When you fetch Strapi API with a slug, instead of an object it returns an array with that data object inside. While in the previous project I fetched API through id, like this:

const post = await fetcher(`${process.env.NEXT_PUBLIC_HCMS_API_URL}/posts/${params.id}`)

But this time I wanted that my post urls were clear with slugified title and I fetched the data by slug. So, the right approach would be something like this: data[0].author.name, data[0].img[0].url

1 Like

In JavaScript almost everything is an object, null and undefined are exceptions. This error occurs when a property is read or a function is called on an undefined variable. Undefined means that a variable has been declared but has not been assigned a value. In JavaScript, properties and functions can only belong to objects. Since undefined is not an object type, calling a function or a property on such a variable causes the TypeError: Cannot read property of undefined.

If you are not sure a variable that will always have some value, the best practice is to check the value of variables for null or undefined before using them. To avoid getting these types of errors, you need to make sure that the variables you are trying to read do have the correct value. This can be done in various ways. You can do if checks before dealing with objects whose values are bound to change:

if (myVar !== undefined) {


if (typeof(myVar) !== 'undefined') {