Update the likes array in a post in the frontend - reactjs

Question

I have a PUT route in the backend for liking posts, it adds the users id to the likes array in the post. This works fine when tested on Postman (by providing the post in the body) and the likes array is updated. However, when the icon is clicked in the frontend, I want the likes array to update but I'm not sure how to update the state for the post. result is showing the response in the frontend with a 200 status code but that's as far as I'm getting.
How can I update the likes array in the frontend?
Post.js
const Post = (props) => {
const [post, setPost] = useState({});
const [error, setError] = useState(false);
const id = props.match.params.id;
const loadSinglePost = (id) => {
read(id).then((data) => {
if (error) {
console.log(data.error);
setError(data.error);
} else {
setPost(data);
console.log(data);
}
});
};
useEffect(() => {
loadSinglePost(id);
}, [props]);
const like = (id) => {
const {user: { _id }, token} = isAuthenticated();
fetch(`${API}/like/${_id}`, {
method: "PUT",
headers: {
"Content-Type": "application/json",
Authorization: `Bearer ${token}`,
},
body: JSON.stringify({
id: id,
}),
})
.then(result => { console.log(result)})
.catch((err) => {
console.log(err);
});
};
return (
<div>
<Navbar />
<div>
<h3>{post && post.title}</h3>
<p>
{post && post.author ? post.author.name : ""}
</p>
<p>{post && post.body}</p>
<h5>{post && post.likes && post.likes.length} likes</h5>
<img
onClick={() => {
like(id);
}}
alt="..."
/>
</div>
</div>
);
};
export default Post;
controllers/post.js
exports.like = (req, res) => {
Post.findByIdAndUpdate(req.body._id, {
$push: {likes: req.profile._id}
}, {new: true}).exec((err, result) => {
if (err) {
return res.status(422).json({error: err})
} else {
return res.json(result)
}
})
}
exports.readById = (req, res) => {
const id = req.params.id
Post.findById(id)
.then(post => res.json(post))
.catch(err => res.status(400).json('Error: ' + err));
}

Answer 1

You can update likes in post in then callback like this:
const like = (id) => {
const {user: { _id }, token} = isAuthenticated();
fetch(`${API}/like/${_id}`, {
method: "PUT",
headers: {
"Content-Type": "application/json",
Authorization: `Bearer ${token}`,
},
body: JSON.stringify({
id: id,
}),
})
.then(result => {
// here update post likes
let updatedPost = {...post}; //to make copy of post
updatedPost.likes = [...updatedPost.likes, id]; //add new id to updatedPost' likes array
setPost(updatedPost); //update post
console.log(result)
})
.catch((err) => {
console.log(err);
});
};
Also from front-end you're sending id key in body:
body: JSON.stringify({
id: id, // here
})
And at back end you're expecting _id
Post.findByIdAndUpdate(req.body._id, { // here
$push: {likes: req.profile._id}
}