Develop Reference

TypeError: res.json is not a function (not able to get fetch data)

I m trying to GET response using fetch API not stuck in a error as I mentioned below. Here's my code
const DefaultLayout = () => {
let history = useHistory()
const callHomePage = async () => {
try {
const res = fetch('http://localhost:4000/api/authenticate', {
method: 'GET',
headers: {
Accept: 'application/json',
'Content-type': 'application/json',
},
credentials: 'include',
})
console.log(res)
const data = await res.json()
console.log(data)
if (!res.status === 200) {
const error = new Error(res.error)
throw error
}
} catch (err) {
console.log(err)
history.push('login')
}
}
Error: TypeError: res.json is not a function
Promise {} shows pending

const DefaultLayout = () => {
let history = useHistory()
const callHomePage = async () => {
try {
const res = await fetch('http://localhost:4000/api/authenticate', {
method: 'GET',
headers: {
Accept: 'application/json',
'Content-type': 'application/json',
},
credentials: 'include',
})
console.log(res)
const data = await res.json()
console.log(data)
if (!res.status === 200) {
const error = new Error(res.error)
throw error
}
} catch (err) {
console.log(err)
history.push('login')
}
}

You need to await the fetch statement and then call the .json method of the response.
const res = await fetch(...)
data = await res.json();
Read more: https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch

converting Promise to async await syntax problem

I want to convert promise in to async await but I cannot find the right syntax for the function that reads the data from the response
export async function getDataFromServer(id) {
try {
const resp = await fetch('/dataget', {
credentials: "same-origin",
mode: "same-origin",
method: 'POST',
headers: { "Content-Type": "application/json" },
body: `${id}`
})
const data = await resp.json()
const handel = await function (data) {
console.log(data);
// render function
renderDataFromServer(data)
}
}
catch (err) {
if (err === "server") return
console.log(err)
}
}

If you remove the unnecessary function declaration it should work:
export async function getDataFromServer(id) {
try {
const resp = await fetch('/dataget', {
credentials: "same-origin",
mode: "same-origin",
method: 'POST',
headers: { "Content-Type": "application/json" },
body: `${id}`
})
const data = await resp.json();
console.log(data);
// render function
return renderDataFromServer(data);
} catch (err) {
if (err === "server") return
console.log(err)
}
}

NextJS: TypeError: Cannot read property 'json' of undefined

I've this code into pages folder on my NextJS environment. It gets data calling an external API Rest, and it's working because the console.log(response); line show me by console the Json API response. The problem I've is that I get this error in browser:
TypeError: Cannot read property 'json' of undefined
Corresponding with this line code:
const data = await res.json();
This is the complete file with the code:
import React from "react";
import fetch from "node-fetch";
const getFetch = async (invoicesUrl, params) => {
fetch(invoicesUrl, params)
.then((response) => {
return response.json();
})
.then((response) => {
console.log(response);
})
.catch((err) => {
console.log(err);
});
};
export const getServerSideProps = async () => {
const invoicesUrl = "https://192.168.1.38/accounts/123456";
const params = {
method: "get",
headers: {
Accept: "application/json",
"Content-Type": "application/json",
},
};
const res = await getFetch(invoicesUrl, params);
const data = await res.json();
console.log("Data Json: ", data);
return { props: { data } };
};
This is the Json API response that I see by console:
{
account: [
{
id: '7051321',
type: 'probe',
status: 'open',
newAccount: [Object],
lastDate: '2020-07-04',
taxExcluded: [Object],
totalRecover: [Object],
documentLinks: []
},
]
}
Any idea how can I solve it?
Thanks in advance.
UPDATE
Here the code working good:
import React from "react";
import fetch from "node-fetch";
const getFetch = async (invoicesUrl, params) => {
return fetch(invoicesUrl, params);
};
export const getServerSideProps = async () => {
const invoicesUrl = "https://192.168.1.38/accounts/123456";
const params = {
method: "get",
headers: {
Accept: "application/json",
"Content-Type": "application/json",
},
};
try {
const res = await getFetch(invoicesUrl, params);
const data = await res.json();
console.log("Data JSON: ", data);
return { props: { data } };
} catch (error) {
console.log("Data ERROR: ", error);
}
};

There are a couple of things you have to change.
const getFetch = async (invoicesUrl, params) => {
fetch(invoicesUrl, params)
.then((response) => {
return response.json();
})
.then((response) => {
console.log(response);
return response; // 1. Add this line. You need to return the response.
})
.catch((err) => {
console.log(err);
});
};
export const getServerSideProps = async () => {
const invoicesUrl = "https://192.168.1.38/accounts/123456";
const params = {
method: "get",
headers: {
Accept: "application/json",
"Content-Type": "application/json",
},
};
const data = await getFetch(invoicesUrl, params);
// const data = await res.json(); 2. Remove this you have already converted to JSON by calling .json in getFetch
console.log("Data Json: ", data); // Make sure this prints the data.
return { props: { data } };
};

You have return statement in wrong place.
When the function is expecting a return. You need to return when the statements are executed not inside the promise then function because it is an async callback function which is not sync with the statement inside getFetchfunction. I hope i have made things clear. Below is the code which will any how return something
import React from "react";
import fetch from "node-fetch";
const getFetch = async (invoicesUrl, params) => {
return fetch(invoicesUrl, params);
};
export const getServerSideProps = async () => {
const invoicesUrl = "https://192.168.1.38/accounts/123456";
const params = {
method: "get",
headers: {
Accept: "application/json",
"Content-Type": "application/json",
},
};
try{
const res = await getFetch(invoicesUrl, params);
console.log("Data Json: ", res);
}catch(error){
console.log("Data Json: ", error);
}
return { props: { res } };
};

Vue - returning the result of a synchronous method

I'm struggling to return the synchronous results of the method below.
I call the method from a different method:
var result = this.getVendor(id)
console.log(result)
Here is the fetch method:
methods: {
async getData(id) {
const response = await fetch(`${API_URL}api/${id}`, {
method: "GET",
headers: {
authorization: `Bearer ${localStorage.token}`
}
})
.then(res => res.json())
.then(data => {
return data;
});
await response;
}
}
How do I return the results response of the getData() function to show in the console?

Async functions Always return a promise.
You can use the await syntax to return it properly.
async getData(id) {
const response = await fetch(`${API_URL}api/${id}`, {
method: "GET",
headers: {
authorization: `Bearer ${localStorage.token}`
}
})
const data = await response.json()
return data
}
You can access the data out of that function anywhere you call it.
let data = null
object.getData(2)
.then(x => {
data = x
})
Also if you are going to use async await make sure to use try and catch to handle any errors that come up.
async getData(id) {
try {
const response = await fetch(`${API_URL}api/${id}`, {
method: "GET",
headers: {
authorization: `Bearer ${localStorage.token}`
}
})
const data = await response.json()
return data
}
} catch(err) {
console.error(err)
}

Async/Await in fetch() how to handle errors

I have stripe async code in my React app, and trying to add error handling in my code but have no idea how to handle it. i know how to do it with .then() but async/await is new to me
EDITED
added .catch() i got errors in network tab in response tab.
but i can log it to console?
submit = async () => {
const { email, price, name, phone, city, street, country } = this.state;
let { token } = await this.props.stripe
.createToken({
name,
address_city: city,
address_line1: street,
address_country: country
})
.catch(err => {
console.log(err.response.data);
});
const data = {
token: token.id,
email,
price,
name,
phone,
city,
street,
country
};
let response = await fetch("/charge/pay", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify(data)
}).catch(err => {
console.log(err.response.data);
});
console.log(response);
if (response.ok)
this.setState({
complete: true
});
};
thanks

Fetch detects only network errors. Other errors (401, 400, 500) should be manually caught and rejected.
await fetch("/charge/pay", headers).then((response) => {
if (response.status >= 400 && response.status < 600) {
throw new Error("Bad response from server");
}
return response;
}).then((returnedResponse) => {
// Your response to manipulate
this.setState({
complete: true
});
}).catch((error) => {
// Your error is here!
console.log(error)
});
If you are not comfortable with this limitation of fetch, try using axios.

var handleError = function (err) {
console.warn(err);
return new Response(JSON.stringify({
code: 400,
message: 'Stupid network Error'
}));
};
var getPost = async function () {
// Get the post data
var post = await (fetch('https://jsonplaceholder.typicode.com/posts/5').catch(handleError));
// Get the author
var response = await (fetch('https://jsonplaceholder.typicode.com/users/' + post.userId).catch(handleError));
if (response.ok) {
return response.json();
} else {
return Promise.reject(response);
}
};

You can either use try/catch just like normal, imperative programming:
try {
let response = await fetch("/charge/pay", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify(data)
});
} catch(error) {
// Error handling here!
}
Or you can mix-and-match .catch() just like you do with promises:
let response = await fetch("/charge/pay", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify(data)
}).catch(function(error) {
// Error handling here!
});

Wrap your await with try catch.
try {
let response = await fetch("/charge/pay", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify(data)
});
console.log(response);
} catch (error) {
console.log(error);
}

This works if server returns { message: "some error" } but I'm trying to get it to support res.statusText too:
const path = '/api/1/users/me';
const opts = {};
const headers = {};
const body = JSON.stringify({});
const token = localStorage.getItem('token');
if (token) {
headers.Authorization = `Bearer ${token}`;
}
try {
const res = await fetch(path, {
method: opts.method || 'GET',
body,
headers
});
if (res.ok) {
return await (opts.raw ? res.text() : res.json());
}
const err = await res.json();
throw new Error(err.message || err.statusText);
} catch (err) {
throw new Error(err);
}

async function loginWithRedirect(payload: {
username: string;
password: string;
}) {
const resp = await (await fetch(`${env.API_URL}/api/auth/login`, {
method: "POST",
headers: {"Content-Type": "application/json"},
body: JSON.stringify(payload),
credentials: "include",
})).json();
if (resp.error) {
dispatch({type: "ERROR", payload: resp.error.message});
} else {
dispatch({type: "LOGIN", payload: resp});
}
}

If response.ok is false you can throw an error then chain catch method after calling your function as follows
async function fetchData(){
const response = await fetch("/charge/pay", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify(data)
});
if(!response.ok){
const message = `An error occured: ${response.status}`;
throw new Error(message);
}
const data = await response.json();
return data;
}
fetchData()
.catch(err => console.log(err.message));

I write promise function for using fetch in async await.
const promisyFetch = (url, options) =>
new Promise((resolve, reject) => {
fetch(url, options)
.then((response) => response.text())
.then((result) => resolve(result))
.catch((error) => reject(error));
});
By the way i can use it easly in async with try catch
const foo = async()=>{
try {
const result = await promisyFetch('url' requestOptions)
console.log(result)
} catch (error) {
console.log(error)
}
}
It was simple example, you could customize promisyFetch function and request options as you wish.

const data = {
token: token.id,
email,
price,
name,
phone,
city,
street,
country
};
axios
.post("/charge/pay", data)
.then(res => {
console.log(res);
})
.catch(err => {
console.log(err.response.data);
});