We Keep Coding

TypeError: Cannot read property 'data' of undefined in JavaScript fetch request

I am getting a TypeError in JavaScript when trying to make a fetch request to "/users/add". The error message says "Cannot read property 'data' of undefined (reading 'data') at register:38:66".
I am making two fetch requests, the first one to get the API key works fine, but the second one to "/users/add" using the API key is causing the error. The response from the second request doesn't seem to have the "data" property.
I have tried logging the response to the console, but I am still not sure what is causing the error.
Here is the relevant code:
let apiKey = null;
fetch("/api-key", {
method: "POST",
headers: {
"Content-Type": "application/json"
}
})
.then(response => response.json())
.then(data => apiKey = data)
.catch(error => console.error(error));
function register() {
let user = document.getElementById("user").value;
let pass = document.getElementById("pass").value;
// Post request to /users/add using the API key
fetch("/users/add", {
method: "POST",
headers: {
"Content-Type": "application/json",
"Authorization": apiKey
},
body: JSON.stringify({
username: user,
password: pass,
api_key: apiKey
})
})
.then(response => {
console.log("Request JSON data:", JSON.parse(response.config.data));
if (!response.ok) {
throw new Error("Failed to add user. Response status: " + response.status);
}
return response.json();
})
.then(data => {
console.log("User added successfully:", data);
})
.catch(error => {
console.error("Error adding user:", error);
});
}
Node.js:
router.route('/add').post((req, res) => {
const username = req.body.username;
const password = req.body.password;
const api_key = req.body.api_key;
bcrypt.hash(password, 10, (err, hashedPassword) => {
if (api_key != real_api_key) {
return res.status(400).json('Error: Incorrect API key');
}
if (err) {
return res.status(400).json('Error: ' + err);
}
const newUser = new User({username, password: hashedPassword, api_key});
newUser.save()
.then(() => res.json('User added!'))
.catch(err => res.status(400).json('Error: ' + err));
});
});

Fetch Error : [TypeError: Network request failed]

I'm using GraphQL in React Native, but it doesn't have much to do with the fact that I'm using RN. When I want to make a request to an endpoint that I want, it throws me the error [TypeError: Network request failed], but only in the function that I want, I tried with some examples, and it responds correctly
I leave 3 functions and the output in the terminal:
const fetchh = async () => {
await fetch('https://api.thegraph.com/subgraphs/name/ensdomains/ens', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify({
query: `
query ($name: String!)
{
domains(first: 75, where: {name_contains: $name, resolvedAddress_not: null, name_ends_with: ".eth"}) {
name
}
}
`,
variables: {
name: 'asd',
},
}),
})
.then(res => res.json())
.then(result => console.log(result, 'RESULTADO'))
.catch(err => console.log(JSON.stringify(err), 'ERROR FETCH1'));
};
====
const fetch2 = async () => {
fetch('https://www.learnwithjason.dev/graphql', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify({
query: `
query GetLearnWithJasonEpisodes($now: DateTime!) {
allEpisode(limit: 10, sort: {date: ASC}, where: {date: {gte: $now}}) {
date
title
guest {
name
twitter
}
description
}
}
`,
variables: {
now: new Date().toISOString(),
},
}),
})
.then(res => res.json())
.then(result => console.log(result, 'FETCH 2'));
};
======
const fetch3 = async () => {
fetch('https://api.thegraph.com/subgraphs/name/ensdomains/ens', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify({
query: `query ($address: ID!)
{
accounts(where: {id: $address}, first: 1000) {
registrations {
domain {
name
subdomains {
name
}
}
expiryDate
}
}
}`,
variables: {
address: '0x9844'.toLowerCase(),
},
}),
})
.then(res => res.json())
.then(result => console.log(result))
.catch(err => console.log(err, 'ERROR FETCH 3'));
};
LOG [TypeError: Network request failed] ERROR FETCH 3
LOG {"line":25338,"column":33,"sourceURL":"localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.welookapp&modulesOnly=false&runModule=true"} ERROR FETCH1
LOG {"data": {"allEpisode": [[Object], [Object], [Object], [Object], [Object], [Object]]}} FETCH 2
The error FETCH 1 and FETCH 3 are the same except for FETCH1 I put JSON.stringify in the .catchIt can also be seen that FETCH 2 brought the results correctly, do you know what could be happening?

React Redux Thunk with callback to another function -- TypeError: Cannot read property 'then' of undefined

I am using react+redux.
I have a modal form with data and images and on success I need to close the modal else display error returned from redux. In the dispatch function I have 1 more callback function to store images to S3. I am returning promise from the redux-thunk but I keep getting "TypeError: Cannot read property 'then' of undefined".
Component
handleSubmit = e => {
e.preventDefault();
if(this.isFieldEmpty()){
this.setState({ message: "All fields are mandatory with at least 1 pic" });
return;
} else {
this.setState({ message: "" });
}
const data = {
name: this.state.name,
description : this.state.description,
points : this.state.points,
attributes : this.state.attributes,
images : this.state.images,
created_by: localStorage.getItem('id'),
}
this.props.createItem(data).then(() => {
this.hideModal();
})
}
const mapDispatchToProps = dispatch => {
return {
createItem: data => {
return dispatch(createItem(data))
},
};
};
Action
const saveItemImages = (images,successcb, failurecb) => {
if(images.length > 0){
const formData = new FormData();
for(var x = 0; x<images.length; x++) {
formData.append('image', images[x])
}
const token = localStorage.getItem('token');
fetch(`${backendUrl}/upload/item-images/`, {
method: "POST",
headers: {
'Authorization': `Bearer ${token}`
},
credentials: 'include',
body: formData
})
.then(res => {
if(res.status === 200){
res.json().then(resData => {
successcb(resData.imagesUrl);
});
}else{
res.json().then(resData => {
failurecb(resData.message);
})
}
})
.catch(err => {
console.log(err);
});
} else {
successcb([]);
}
}
export const createItem = data => { return (dispatch) => {
saveItemImages(data.images, imagesUrl => {
data.images = imagesUrl;
return fetch(`${backendUrl}/admin/createItem`, {
method: 'POST',
headers: {
'Accept': 'application/json, text/plain, */*',
'Content-Type': 'application/json',
'Authorization': `Bearer ${data.token}`
},
credentials: 'include',
body: JSON.stringify(data)
})
.then(res => {
if(res.status === 200){
res.json().then(resData => {
dispatch({
type: ADMIN_CREATE_ITEM_SUCCESS,
payload: resData
})
return true;
});
}else{
console.log("Save failed");
res.json().then(resData => {
dispatch({
type: ADMIN_CREATE_ITEM_FAILED,
payload: {
message: resData.message
}
})
})
}
})
.catch(err => {
dispatch({
type: ADMIN_CREATE_ITEM_FAILED,
payload: {
message: `Internal Error -- ${err}`
}
})
});
}, failedMessage => {
let payload = {responseMessage: failedMessage}
dispatch({
type: ADMIN_CREATE_ITEM_FAILED,
payload: payload
})
});
};
};
Thanks in advance for any help

You should return a Promise to create async flow for the action like this:
export const createItem = data => dispatch => new Promise((resolve, reject) => {
// do something was a success
resolve();
// do something was a fail
reject();
});

React Redux promise error - (...).then is not a function

Had a look for this in the questions that offered but this was the closest and it didnt really address my problem.
I have a code block (detailed a little way down the page) as part of a larger fetch block.. it gets to this codeblock and also runs fine if this code block is commented out i.e it carrys out a successful fetch etc and returns a JWT no problem but... add this block in and i get the following error:
TypeError: (0 , _localStorageDropDowns.confirmSelectDataExistance)(...).then is not a function
It is referring to this function in another folder (imported correctly)..
export const confirmSelectDataExistance = () => {
const companyStateShortNameJson = localStorage.getItem(COMPANYSTATESHORTNAME)
const statesJson = localStorage.getItem(STATES)
const suburbLocationsJson = localStorage.getItem(LOCATIONS)
if (companyStateShortNameJson || statesJson || suburbLocationsJson) {
console.log('something exists in localstorage')
return true
}
console.log('nothing in localstorage')
return false
}
simple function - returns true or false.
and here is the code block -its failing on the first line:
return confirmSelectDataExistance().then(isConfirmed => {
if (!isConfirmed) {
dispatch({ type: REQUEST_SELECT_DATA })
console.log('gets here!', isConfirmed)
const token = getJwt()
const headers = new Headers({
'Authorization': `Bearer ${token}`
})
const retrieveSelectData = fetch('/api/SelectData/SelectData', {
method: 'GET',
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
})
.then(handleErrors)
.then(response => response.json())
.then(selectData => {
dispatch({ type: RECEIVE_SELECT_DATA, payload: selectData })
saveSelectData(selectData)
});
return saveSelectData(selectData);
}
})
From my limited experience the "confirmSelectDataExistance" is a function so why is it saying that its not?
Finally here is the whole action in its entirety so you can see how it that block is called.. as I said - comment the block out and it works perfectly..
export const requestLoginToken = (username, password) =>
(dispatch, getState) => {
dispatch({ type: REQUEST_LOGIN_TOKEN, payload: username })
const payload = {
userName: username,
password: password,
}
const task = fetch('/api/jwt', {
method: 'POST',
body: JSON.stringify(payload),
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
})
.then(handleErrors)
.then(response => response.json())
.then(data => {
dispatch({ type: RECEIVE_LOGIN_TOKEN, payload: data })
saveJwt(data)
return confirmSelectDataExistance().then(isConfirmed => {
if (!isConfirmed) {
dispatch({ type: REQUEST_SELECT_DATA })
console.log('gets here!', isConfirmed)
const token = getJwt()
const headers = new Headers({
'Authorization': `Bearer ${token}`
})
const retrieveSelectData = fetch('/api/SelectData/SelectData', {
method: 'GET',
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
})
.then(handleErrors)
.then(response => response.json())
.then(selectData => {
dispatch({ type: RECEIVE_SELECT_DATA, payload: selectData })
saveSelectData(selectData)
});
return saveSelectData(selectData);
}
})
})
.catch(error => {
clearJwt()
console.log('ERROR - LOGIN!',error)
})
addTask(task)
return task
}
EDIT
I have finally got this to work after hacking away for hours.. Here is the finished action:
export const requestLoginToken = (username, password) =>
(dispatch, getState) => {
dispatch({ type: REQUEST_LOGIN_TOKEN, payload: username })
const payload = {
userName: username,
password: password,
}
const task = fetch('/api/jwt', {
method: 'POST',
body: JSON.stringify(payload),
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
})
.then(handleErrors)
.then(response => response.json())
.then(data => {
dispatch({ type: RECEIVE_LOGIN_TOKEN, payload: data })
saveJwt(data)
// Now check local storage for dropdown data..
if (!confirmSelectDataExistance()) {
dispatch({ type: REQUEST_SELECT_DATA })
const token = JSON.stringify(data)
const headers = new Headers({
'Authorization': `Bearer ${token}`
})
const retrieveSelectData = fetch('/api/SelectData/SelectData', {
method: 'GET',
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
})
.then(handleErrors)
.then(response => response.json())
.then(selectData => {
dispatch({ type: RECEIVE_SELECT_DATA, payload: selectData })
saveSelectData(selectData)
});
}
})
.catch(error => {
clearJwt()
console.log('ERROR - LOGIN!', error)
})
addTask(task)
return task
}
and here is the function it calls:
export const confirmSelectDataExistance = () => {
const companyStateShortNameJson = localStorage.getItem(COMPANYSTATESHORTNAME)
const statesJson = localStorage.getItem(STATES)
const suburbLocationsJson = localStorage.getItem(LOCATIONS)
if (companyStateShortNameJson || statesJson || suburbLocationsJson) {
console.log('something exists in localstorage')
return true
}
console.log('nothing in localstorage')
return false
}
The one thing I changed from the other attempts is that I used "data" instead of calling "getJwt()". I then used the line:
const token = JSON.stringify(data)
to obtain the JWT I just got.
In the end I used #Karin s answer and ran with that. (upvoted by me)

The error is not saying that confirmSelectDataExistance is not a function, it's saying that then isn't a function on what is returned from it, which is a boolean (it would be equivalent to false.then(...), which doesn't work).
If seems like you're trying to use then as a conditional. In that case a simple if statement should work:
if (confirmSelectDataExistance()) {
// do things if it returns true
} else {
// do things if it returns false
}

export const confirmSelectDataExistance = () => {
return new Promise(function (resolve, reject) {
const companyStateShortNameJson = localStorage.getItem(COMPANYSTATESHORTNAME)
const statesJson = localStorage.getItem(STATES)
const suburbLocationsJson = localStorage.getItem(LOCATIONS)
if (companyStateShortNameJson || statesJson || suburbLocationsJson) {
console.log('something exists in localstorage')
resolve(true)
}
console.log('nothing in localstorage')
reject(false)
})
}

Try something like this:
export const confirmSelectDataExistance = new Promise((resolve, reject) => {
const companyStateShortNameJson = localStorage.getItem(COMPANYSTATESHORTNAME);
const statesJson = localStorage.getItem(STATES);
const suburbLocationsJson = localStorage.getItem(LOCATIONS);
if (companyStateShortNameJson || statesJson || suburbLocationsJson) {
console.log('something exists in localstorage');
resolve(true);
}
console.log('nothing in localstorage');
reject(false); // or resolve(false) if you want handle this situation inside then block also
});

Javascript: Fetch DELETE and PUT requests

I have gotten outside of GET and POST methods with Fetch. But I couldn't find any good DELETE and PUT example.
So, I ask you for it. Could you give a good example of DELETE and PUT methods with fetch. And explain it a little bit.

Here is a fetch POST example. You can do the same for DELETE.
function createNewProfile(profile) {
const formData = new FormData();
formData.append('first_name', profile.firstName);
formData.append('last_name', profile.lastName);
formData.append('email', profile.email);
return fetch('http://example.com/api/v1/registration', {
method: 'POST',
body: formData
}).then(response => response.json())
}
createNewProfile(profile)
.then((json) => {
// handle success
})
.catch(error => error);

Ok, here is a fetch DELETE example too:
fetch('https://example.com/delete-item/' + 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: https://www.someapi/id

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 https://link.medium.com/4ZvwCordCW
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 https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch > Fetch_API.

Some examples:
async function loadItems() {
try {
let response = await fetch(`https://url/${AppID}`);
let result = await response.json();
return result;
} catch (err) {
}
}
async function addItem(item) {
try {
let response = await fetch("https://url", {
method: "POST",
body: JSON.stringify({
AppId: appId,
Key: item,
Value: item,
someBoolean: false,
}),
headers: {
"Content-Type": "application/json",
},
});
let result = await response.json();
return result;
} catch (err) {
}
}
async function removeItem(id) {
try {
let response = await fetch(`https://url/${id}`, {
method: "DELETE",
});
} catch (err) {
}
}
async function updateItem(item) {
try {
let response = await fetch(`https://url/${item.id}`, {
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('https://reqres.in/api/users', + 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('https://reqres.in/api/users' + id, {
method: 'DELETE',
})
.then(res => {
return res.json()
})
.then(data => console.log(data))
Note: I'm using dummy api here.

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('https://reqres.in/api/users', {
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))

Here are examples for Delete and Put for React & redux & ReduxThunk with Firebase:
Update (PUT):
export const updateProduct = (id, title, description, imageUrl) => {
await fetch(`https://FirebaseProjectName.firebaseio.com/products/${id}.json`, {
method: "PATCH",
header: {
"Content-Type": "application/json",
},
body: JSON.stringify({
title,
description,
imageUrl,
}),
});
dispatch({
type: "UPDATE_PRODUCT",
pid: id,
productData: {
title,
description,
imageUrl,
},
});
};
};
Delete:
export const deleteProduct = (ProductId) => {
return async (dispatch) => {
await fetch(
`https://FirebaseProjectName.firebaseio.com/products/${ProductId}.json`,
{
method: "DELETE",
}
);
dispatch({
type: "DELETE_PRODUCT",
pid: ProductId,
});
};
};

const DeleteBtn = (id) => {
fetch(`http://localhost:8000/blogs/${id}`, {
method: "DELETE"
})
.then(() => {
navigate('/');
});
}
<button onClick={(event) => { DeleteBtn(blog.id)} }>delete</button>