Ok, here is a fetch DELETE example too:

fetch(' + id, {
  method: 'DELETE',
})
.then(res => res.text()) // or res.json()
.then(res => console.log(res))

For put method we have:

const putMethod = {
 method: 'PUT', // Method itself
 headers: {
  'Content-type': 'application/json; charset=UTF-8' // Indicates the content 
 },
 body: JSON.stringify(someData) // We send data in JSON format
}

// make the HTTP put request using fetch api
fetch(url, putMethod)
.then(response => response.json())
.then(data => console.log(data)) // Manipulate the data retrieved back, if we want to do something with it
.catch(err => console.log(err)) // Do something with the error

Example for someData, we can have some input fields or whatever you need:

const someData = {
 title: document.querySelector(TitleInput).value,
 body: document.querySelector(BodyInput).value
}

And in our data base will have this in json format:

{
 "posts": [
   "id": 1,
   "title": "Some Title", // what we typed in the title input field
   "body": "Some Body", // what we typed in the body input field
 ]
}

For delete method we have:

const deleteMethod = {
 method: 'DELETE', // Method itself
 headers: {
  'Content-type': 'application/json; charset=UTF-8' // Indicates the content 
 },
 // No need to have body, because we don't send nothing to the server.
}
// Make the HTTP Delete call using fetch api
fetch(url, deleteMethod) 
.then(response => response.json())
.then(data => console.log(data)) // Manipulate the data retrieved back, if we want to do something with it
.catch(err => console.log(err)) // Do something with the error

In the url we need to type the id of the of deletion:

Just Simple Answer. FETCH DELETE

function deleteData(item, url) {
  return fetch(url + '/' + item, {
    method: 'delete'
  })
  .then(response => response.json());
}

Here is good example of the CRUD operation using fetch API:

“A practical ES6 guide on how to perform HTTP requests using the Fetch API” by Dler Ari

Here is the sample code I tried for PATCH or PUT

function update(id, data){
  fetch(apiUrl + "/" + id, {
    method: 'PATCH',
    body: JSON.stringify({
     data
    })
  }).then((response) => {
    response.json().then((response) => {
      console.log(response);
    })
  }).catch(err => {
    console.error(err)
  })

For DELETE:

function remove(id){
  fetch(apiUrl + "/" + id, {
    method: 'DELETE'
  }).then(() => {
     console.log('removed');
  }).catch(err => {
    console.error(err)
  });

For more info visit Using Fetch - Web APIs | MDN > Fetch_API.

Some examples:

async function loadItems() {
        try {
            let response = await fetch(`);
            let result = await response.json();
            return result;
        } catch (err) {
        }
    }

    async function addItem(item) {
        try {
            let response = await fetch("", {
                method: "POST",
                body: JSON.stringify({
                    AppId: appId,
                    Key: item,
                    Value: item,
                    someBoolean: false,
                }),
                headers: {
                    "Content-Type": "application/json",
                },
            });
            let result = await response.json();
            return result;
        } catch (err) {
        }
    }

    async function removeItem(id) {
        try {
            let response = await fetch(` {
                method: "DELETE",
            });
        } catch (err) {
        }
    }

    async function updateItem(item) {
        try {
            let response = await fetch(` {
                method: "PUT",
                body: JSON.stringify(todo),
                headers: {
                    "Content-Type": "application/json",
                },
            });
        } catch (err) {
        }
    }

Let me simplify this, you can straight up copy the code.

This is for PUT method :

fetch(' + id {
  method: 'PUT',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    name: 'user'
  })
})
.then(res => {
  return res.json()
})
.then(data => console.log(data))

and this is for DELETE :

fetch(' + id, {
  method: 'DELETE',
})
.then(res => {
  return res.json()
}) 
.then(data => console.log(data))

Note: I'm using dummy api here.

Here are examples for Delete and Put for React & redux & ReduxThunk with Firebase:

Update (PUT):

export const updateProduct = (id, title, description, imageUrl) => {
    await fetch(` {
  method: "PATCH",
  header: {
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    title,
    description,
    imageUrl,
  }),
});

dispatch({
  type: "UPDATE_PRODUCT",
  pid: id,
  productData: {
    title,
    description,
    imageUrl,
  },
});
};
};

Delete:

export const deleteProduct = (ProductId) => {
  return async (dispatch) => {
await fetch(
  `
  {
    method: "DELETE",
  }
);
dispatch({
  type: "DELETE_PRODUCT",
  pid: ProductId,
});
  };
};

This is what worked for me when using the PUT method. This method allows me to effectively update the 1st item using my first name:

fetch(' {
  method: 'PUT',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    id: 1,
    first_name: 'Anthony'
  })
})
.then(res => {
  return res.json()
})
.then(data => console.log(data))