I'm currently trying to fetch data from public API about a country and its neighboring countries to render on my html.
renderCountry( ) is a function to implement on my html with the data I will receive.
I also excluded some unnecessary codes, which I believe is not major in this particular case.
This is how I fetch data:
const getCountryAndNeighbour = function(country) {
fetch(`https://restcountries.com/v2/name/${country}`)
.then(response => response.json())
.then(data => {
renderCountry(data[0]);
const neighbour = data[0].borders;
neighbour.forEach(country => {
fetch(`https://restcountries.com/v2/alpha/${country}`)
.then(response => response.json())
.then(data => renderCountry(data, `neighbour`))
});
})
}
Here, you will see callback hell architecture. Any idea for escape from that?
Thanks in advance.
You can try using async/await. You would add async before the function keyword and add await as needed. See below to see this in action:
const getCountryAndNeighbour = async function (country) {
const res = await fetch(`https://restcountries.com/v2/name/${country}`)
const data = await res.json();
renderCountry(data[0]);
const neighbour = data[0].borders;
await Promise.all(
neighbour.map(async country => {
let response = await fetch(`https://restcountries.com/v2/alpha/${country}`)
response = await response.json();
return renderCountry(response, 'neighbour');
});
);
}
You can rewrite it using async/await
eg.
const getCountryAndNeighbour = async country => {
const response = await fetch(`https://restcountries.com/v2/name/${country}`);
const data = await response.json();
renderCountry(data[0]);
const neighbour = data[0].borders;
neighbour.forEach(async country => {
const response = await fetch(`https://restcountries.com/v2/alpha/${country}`)
const data = await response.json();
renderCountry(data, `neighbour`);
});
};
Please note that forEach will run all promises in the same time.
If you want to run one by one you should use eg. for loop or some util like Bluebird.map which allows you to specify a concurrency
Good luck!
This will do using Async/await
async function getCountryData(country) {
const response = await fetch(`https://restcountries.com/v2/name/${country}`);
return await response.json();
}
async function getNeighbourData(country) {
const response = await fetch(`https://restcountries.com/v2/alpha/${country}`);
return await response.json();
}
async function getCountryAndNeighbour(country) {
const data = await getCountryData(country);
const neighbourCountries = data[1].borders;
for (const neighbour of neighbourCountries) {
const response = await getNeighbourData(neighbour);
console.log(response);
}
}
Add the necessary validations when checking [0]/[1] in your function.
Related
I'm facing a probably super easy to solve problem regarding fetching.
I'd like to fetch some json datas and store it in a variable to access it later.
The problem is that I always ends up getting undefined in my variable. What's the way to do to deal with that kind of data storing ?
Here's my code.
const fetchCities = () => {
fetch('cities.json')
.then(response => response.json())
.then(data => {
return data;
});
}
let cities = fetchCities();
console.log(cities)
Already looked up for answers but couldn't find a way to do. Thanks !
You could do this very simply with async/await like this:
const fetchCities = async () => {
let cities = await fetch('cities.json');
return cities.json();
};
let cities = await fetchCities();
console.log(cities);
Sending a fetch request takes time, so the console.log works before the data arrives.
The best way to deal with fetch is using async functions and await like so:
const fetchCities = ()=>{
return fetch('cities.json');
}
async function main(){
try {
const res = await fetchCities();
const data = await res.json();
// handle the data here, this will work only after the data arrival
console.log(data);
} catch (err) {
console.log(err);
}
}
main();
Note: await can only be used in async functions, that's the main purpose of the main function.
Or if you want to use .then:
const fetchCities = ()=>{
return fetch('cities.json');
}
function main(){
fetchCities()
.then(res => res.json())
.then(data => {
// handle the data here, all you code should be here
})
.catch (err => console.log(err));
}
main();
I would like to get http status code after response.json to use it in my logic later, can I do something with it?
function apiRequest(path, options) {
fetch("api/" + path, options)
.then(response => response.json())
.then(data => {
let res = {
code: 200 //I want to put http status code here,
data: data
}
return res;
})
}
This is slightly tricky using then (as you are currently doing) because you want to get data directly from the response (which is a promise) and some more data from the parsed body (which is another promise).
So you can wrap the status and the data promise in a Promise.all and return that from the first then:
const apiRequest = () => {
const url = "//swapi.dev/api/planets/1/";
fetch(url)
.then((response) => Promise.all([response.status, response.json()]))
.then(([status, data]) => console.log({status, data}))
}
… but it would be easier to use async/await syntax and ditch the callbacks and you then only have to worry about a single function (and therefore scope) rather than multiple.
const apiRequest = async () => {
const url = "//swapi.dev/api/planets/1/";
const response = await fetch(url);
const data = await response.json();
const status = response.status;
console.log({status, data})
}
As an alternative you could consider async/await. That way you have access to response and data at the same time more easily.
async function apiRequest(path, options) {
const response = await fetch("api/" + path, options)
const data = await response.json()
let res = {
code: response.status,
data: data
}
// Do something with res
}
Try this
function apiRequest(path, options) {
fetch("api/" + path, options)
.then(response => Promise.all([Promise.resolve(response.status), response.json()]))
.then(([status, data]) => {
let res = {
code: status //I want to put http status code here,
data: data
}
return res;
})
}
you can git it in the first then before you return response.json something like this
function apiRequest(path, options) {
fetch("api/")
.then((response) => {
let status = response.status;
console.log("status", status);
return response.json();
})
.then((data) => {
console.log(data);
});
}
apiRequest();
I wonder if there is a way to access data from then on the next one? Code looks like this:
fetch(`http://localhost:3003/users/${userObject.id}`)
.then(res => res.json())
.then(user => {
...
})
.then(???)
and in second then I have all the needed info about the user. When I put everything in second then it works, but code is very messy and repetitive and I would like to put some things into function. Unfortunately, in that case, I don't have access to some data...
Any ideas? Thanks!
You can pass an argument to the next promise by returning it from the previous one.
fetch(`http://localhost:3003/users/${userObject.id}`)
.then(res => res.json())
.then(user => {
return user.id;
})
.then(userId => {
console.log('user id is:', userId);
});
Also, you can accomplish same result by using async programming like bellow:
async function fetchSomeData() {
var res = await fetch(`http://localhost:3003/users/${userObject.id}`);
var user = await res.json();
return user;
}
fetchSomeData().then(user => {
console.log('user id is:', user.id)
});
but code is very messy and repetitive and I would like to put some
things into function
Just use async/await syntax, it's much more understandable.
(async() => {
const request = await fetch(`http://localhost:3003/users/${userObject.id}`);
const result = await request.json();
// proceed to do whatever you want with the object....
})();
This is a self-executing function, but you can also declare this in the following way:
const myFunc = async() => {
const request = await fetch(`http://localhost:3003/users/${userObject.id}`);
const result = await request.json();
// your logic here or you can return the result object instead;
};
or even without arrow functions:
const myFunc = async function() {
const request = await fetch(`http://localhost:3003/users/${userObject.id}`);
const result = await request.json();
console.log(result.id);
};
I need some help returning a promise. I don't get why I am not getting the players value
The code
const playerSelectName = document.getElementById('sel1');
const playerSelectPosition = document.getElementById('sel2');
const playerSelectAge = document.getElementById('sel3');
const searchButton = document.getElementById('search-btn');
async function getPlayers() {
const response = await fetch('https://football-players-b31f2.firebaseio.com/players.json?print=pretty');
const playersObject = await response.json();
return playersObject;
}
searchButton.addEventListener('click', async () => {
const players = await getPlayers();
let [ name, position, age ] = [ playerSelectName.value, playerSelectPosition.value, playerSelectAge.value ];
yersObject.filter((playerAge) => {});
});
I cant get to access the code inside my listener function of the value players
the problem was in destructuring check the below snippet. I hope this will solve the issue . Also please update what you are trying to achieve in filter so i can add on the solution.
I didnt understood what are you trying to do in destructure part and after that filter
async function getPlayers() {
const response = await fetch('https://football-players-b31f2.firebaseio.com/players.json?print=pretty');
const playersObject = await response.json();
return playersObject;
}
const searchButton = document.getElementById('search-btn');
searchButton.addEventListener('click', async () => {
const players = await getPlayers();
players.forEach(player => {
const {name, nationality, position} = player
console.log(name, nationality, position)
})
});
<button id='search-btn'>
Load Results
</button>
Here's a simple example accessing the players to help get you started.
async function getPlayers() {
const response = await fetch('https://football-players-b31f2.firebaseio.com/players.json?print=pretty');
return response.json();
}
(async () => {
const players = await getPlayers();
console.log(players)
})();
I need to merge data from API. I do a first call to an endpoint that gives me a list of ids, then I do a request for each id. My goal is to return a list with the responses of all requests but I lost myself in promises ...
My code runs on NodeJS. Here is the code :
const fetch = require('node-fetch')
const main = (req, res) => {
fetch('ENDPOINT_THAT_GIVES_LIST_OF_IDS')
.then(response => response.json())
.then(response => {
parseIds(response)
.then(data => {
console.log(data)
res.json(data)
// I want data contains the list of responses
})
})
.catch(error => console.error(error))
}
const getAdditionalInformations = async function(id) {
let response = await fetch('CUSTOM_URL&q='+id, {
method: 'GET',
});
response = await response.json();
return response
}
const parseIds = (async raw_ids=> {
let ids= []
raw_ids.forEach(function(raw_id) {
let informations = {
// Object with data from the first request
}
let additionalInformations = await
getAdditionalInformations(raw_id['id'])
let merged = {...informations, ...additionalInformations}
ids.push(merged)
})
return ids
})
main()
I get this error : "await is only valid in async function" for this line :
let additionalInformations = await getAdditionalInformations(raw_id['id'])
Help me with promise and async/await please.
You're almost there, just a slight bit of error here with your parentheses:
// notice the parentheses'
const parseIds = async (raw_ids) => {
let ids= []
raw_ids.forEach(function(raw_id) {
let informations = {
// Object with data from the first request
}
let additionalInformations = await getAdditionalInformations(raw_id['id'])
let merged = {...informations, ...additionalInformations}
ids.push(merged)
})
return ids
}
You are missing an async after forEach
const parseIds = (async raw_ids=> {
let ids= []
raw_ids.forEach(async function(raw_id) {
let informations = {
// Object with data from the first request
}
let additionalInformations = await
getAdditionalInformations(raw_id['id'])
let merged = {...informations, ...additionalInformations}
ids.push(merged)
})
return ids
})
One suggestion: you are mixing promises (.then()) with async/await. Prefer async/await is more readable.
Note that getAdditionalInformations inside forEach doesn't wait for it to be done before going to the next entry of the array.
You can use plain old for(var i=0; .... instead