I'm using Next.js / React.js. I'm using this API to get a specific country.
There's an array on this response called borders, for example.
borders: [
"CAN",
"MEX",
],
There's an end point to get the data based on a border, for example.
https://restcountries.eu/rest/v2/alpha/can
How would I get the data both borders, i.e. each element in the borders array? It's two API calls that I've tried to make in a loop, but I get undefined.
export async function getServerSideProps(context) {
const { name } = context.params;
const res = await fetch(`https://restcountries.eu/rest/v2/name/${name}?fullText=true`)
const countryRes = await res.json();
const country = countryRes[0];
// Get the borders
const borders = country.borders;
// I'm making an API call to each element in array
const borderCountr = borders.forEach(border => {
fetch(`https://restcountries.eu/rest/v2/alpha/${border}`);
});
console.log(borderCountr); // undefinded
if (!country) {
return {
notFound: true,
}
}
return {
props: { country }
}
}
A good approach would be using Promise.all, to be sure that each fetch is correctly executed. Also, you need to make those calls async. something like:
const borderCountr = await Promise.all(
borders.map(async (border) => {
const response = await fetch(`https://restcountries.eu/rest/v2/alpha/${border}`);
return await response.json();
})
);
console.log(borderCountr[0], borderCountr[1]);
// I'm making an API call to each element in array
const borderCountr = borders.forEach(border => {
fetch(`https://restcountries.eu/rest/v2/alpha/${border}`);
});
This is not awaited (you do not await for ANY of the fetch results) that mens, the code executes here, and without waiting for the fetches to finish - executed the next lines.
As forEach returns undefined, that is your variable content.
Related
My app has a search bar where the user types in a word and clicks search. Upon click, the app fetches the definition of that word from an open dictionary API, and then updates the parent component's state to reflect the results. The component is then supposed to render the results by passing that as a prop to a presentational child component.
However, it looks like the state gets set before the fetch call has the time to return the data. So the search results are not rendered until the search button is clicked again, causing confusion.
I have tried resolving this by making my function asynchronous (Dictionary.search refers to an imported function which handles the fetch and returns the result in the form of an array):
async search(term) {
const results = await Dictionary.search(term);
this.setState({ searchTerm: term, results: results });
}
However this only works some of the time. For longer searches, it doesn't wait before updating the state and re-rendering.
I have done some googling and came across this suggestion, but it also doesn't work:
search = (term) => {
const dictionarySearch = async (term) => {
const results = await Dictionary.search(term);
this.setState({ searchTerm: term, results: results });
};
dictionarySearch(term);
};
EDITED TO ADD: Here is the Dictionary.search code, along with its helper function:
//Create an empty array in which the results of the API call will be stored
let results = [];
const Dictionary = {
search(term) {
//Url with our search term and API key:
const url = `https://www.dictionaryapi.com/api/v3/references/collegiate/json/${term}?key=${api_key}`;
//Fetch the results from Merriam Webster API:
fetch(url)
.then((response) => {
//Catch an error from their server
if (!response.ok) {
throw new Error("Network response was not ok");
}
//Return javaScript object version of the response
return response.json();
})
.then((jsonResponse) => {
//Perform the helper function on the javascript object and return the result (array)
return shortDef(jsonResponse);
})
//Catch any other errors than a server error
.catch((error) => {
console.error(
"There has been a problem with your fetch operation:",
error
);
});
//Create a copy of the results array
let returnResults = results.slice();
//Reset the original array to an empty array
results = [];
//Return the copy
return returnResults;
},
};
//Helper function to extract only certain info from the API
function shortDef(response) {
response.forEach((object) => {
//Create a new object for each object int he response array
let result = { word: "", type: "", definitions: [] };
//Add the word and type to the object
result.word = object.hwi.hw;
result.type = object.fl;
//Add the definitions to the object. There may be several, so it is pushed to an array.
let defs = object.shortdef;
defs.forEach((def) => {
result.definitions.push(def);
});
//Add the object to the array of API results
results.push(result);
});
//Return the list of results
return results;
}
I don't want to call the API in the ComponentDidMount, because it should get called every time the user presses "search". I also would prefer not to use useEffect, as it would mean refactoring my entire component from a class to a function.
Is there no way to have the setState in a class component wait for an asynchronous task to complete?
The problem is that your Dictionary.search function immediately returns, because it does not wait until the .then block resolves. Change it to an async function and await the fetch of the url. It should look like this:
const Dictionary = {
// Make search an async function
search: async term => {
const url = `https://www.dictionaryapi.com/api/v3/references/collegiate/json/${term}?key=${api_key}`;
// Await the results
await fetch(url)
.then(response => {
// ...
})
.then(jsonResponse => {
// ...
})
.catch(error => {
// ...
});
return;
},
};
I'm developing the front-end for my spring boot application. I set up an initial call wrapped in a useEffect() React.js function:
useEffect(() => {
const getData = async () => {
try {
const { data } = await fetchContext.authAxios.get(
'/myapi/' + auth.authState.id
);
setData(data);
} catch (err) {
console.log(err);
}
};
getData();
}, [fetchContext]);
The data returned isn't comprehensive, and needs further call to retrieve other piece of information, for example this initial call return an employee id, but if I want to retrieve his name and display it I need a sub-sequential call, and here I'm experiencing tons of issues:
const getEmployeeName = async id => {
try {
const name = await fetchContext.authAxios.get(
'/employeeName/' + id
);
console.log((name["data"])); // <= Correctly display the name
return name["data"]; // return an [Object promise],
} catch (err) {
console.log(err);
}
};
I tried to wrap the return call inside a Promise.resolve() function, but didn't solve the problem. Upon reading to similar questions here on stackoverflow, most of the answers suggested to create a callback function or use the await keyword (as I've done), but unfortunately didn't solve the issue. I admit that this may not be the most elegant way to do it, as I'm still learning JS/React I'm open to suggestions on how to improve the api calls.
var output = Object.values(data).map((index) =>
<Appointment
key={index["storeID"].toString()}
// other irrelevant props
employee={name}
approved={index["approved"]}
/>);
return output;
Async functions always return promises. Any code that needs to interact with the value needs to either call .then on the promise, or be in an async function and await the promise.
In your case, you should just need to move your code into the existing useEffect, and setState when you're done. I'm assuming that the employeeID is part of the data returned by the first fetch:
const [name, setName] = useState('');
useEffect(() => {
const getData = async () => {
try {
const { data } = await fetchContext.authAxios.get(
"/myapi/" + auth.authState.id
);
setData(data);
const name = await fetchContext.authAxios.get(
'/employeeName/' + data.employeeID
);
setName(name.data);
} catch (err) {
console.log(err);
}
};
getData();
}, [fetchContext]);
// ...
var output = Object.values(appointmentsData).map((index) =>
<Appointment
key={index["storeID"].toString()}
// other irrelevant props
employee={name}
approved={index["approved"]}
/>);
return output;
Note that the above code will do a rerender once it has the data (but no name), and another later when you have the name. If you want to wait until both fetches are complete, simply move the setData(data) down next to the setName
Im beginner and trying to better understand API calls.
I want to make a call to a bible api that retrieves all books.
I then need to make a call to the same api with the book # to retrieve all chapters for requested book.
I then want to display a list of the books along with the chapters.
To this I made a utility function that loops through the books and returns the chapters. This is where it breaks.
I was able to retrieve the books and display them. But I am stuck as to how the make the second API call. I keep getting an error that I cannot serialize object Promise.
Also what is the best way to console log here in Next? Im not sure how to go about seeing what its being returned.
Here is what I have so far:
export default function Home(props) {
console.log(props);
return (
<div className="container">
<div>{/** display books & chapters */}</div>
</div>
);
}
export async function getStaticProps() {
// get all books
const reqBooks = await fetch(`https://getbible.net/v1/web/books.json`);
const resBooks = await reqBooks.json();
// convert to array of objs
const books = await Object.entries(resBooks);
const chapters = await getChapters(books);
return {
props: {
books,
chapters,
},
};
}
// utility... loop through books and make api calls to get chapters for each book
async function getChapters(books) {
const chaptersArr = [];
books.map((item, idx) => {
//
let url = item[1].url;
let bookChapters = fetch(url).then(response => response.json().then(data => data));
arr.push(bookChapters);
});
return chaptersArr;
}
The problem is that you're pushing promises into an array, not the values inside the promises. Instead of using that array, you can return in the map directly, and use Promise.all to get the values out. (You could use the array too, but there's no need for it since you're using a map). I lifted the getBooks call into its own function for clarity here, but the important change is what's going on in getChapters in the map:
async function getBooks () {
const res = await fetch('https://getbible.net/v1/web/books.json')
const json = await res.json()
return Object.entries(json)
}
async function getChapters (books) {
const chapters = await Promise.all(
books.map(async (item) => {
const url = item[1].url
const res = await fetch(url)
const json = await res.json()
return json
})
)
return chapters
}
export async function getStaticProps() {
const books = await getBooks()
const chapters = await getChapters(books)
return {
props: {
books,
chapters,
},
}
}
You can test this in plain Node (assuming node-fetch or a similar package) or the browser outside of Next with something like:
getStaticProps().then(data => {
console.log(JSON.stringify(data, null, 2))
})
Is there any way I can make the below code run synchronously in a way where I can get all of the productLine ids and then loop through and delete all of them, then once all of this is complete, get all of the productIds and then loop through and delete all of them?
I really want to be able to delete each set of items in batch, but the next section can't run until the first section is complete or there will be referential integrity issues.
// Delete Product Lines
axios.get('https://myapi.com/ProductLine?select=id')
.then(function (response) {
const ids = response.data.value
ids.forEach(id => {
axios.delete('https://myapi.com/ProductLine/' + id)
})
})
.catch(function (error) {
})
// Delete Products (I want to ensure this runs after the above code)
axios.get('https://myapi.com/Product?select=id')
.then(function (response) {
const ids = response.data.value
ids.forEach(id => {
axios.delete('https://myapi.com/Product/' + id)
})
})
.catch(function (error) {
})
There's a lot of duplication in your code. To reduce code duplication, you can create a helper function that can be called with appropriate arguments and this helper function will contain code to delete product lines and products.
async function deleteHelper(getURL, deleteURL) {
const response = await axios.get(getURL);
const ids = response.data.value;
return Promise.all(ids.map(id => (
axios.delete(deleteURL + id)
)));
}
With this helper function, now your code will be simplified and will be without code duplication.
Now to achieve the desired result, you could use one of the following ways:
Instead of two separate promise chains, use only one promise chain that deletes product lines and then deletes products.
const prodLineGetURL = 'https://myapi.com/ProductLine?select=id';
const prodLineDeleteURL = 'https://myapi.com/ProductLine/';
deleteHelper(prodLineGetURL, prodLineDeleteURL)
.then(function() {
const prodGetURL = 'https://myapi.com/Product?select=id';
const prodDeleteURL = 'https://myapi.com/Product/';
deleteHelper(prodGetURL, prodDeleteURL);
})
.catch(function (error) {
// handle error
});
Use async-await syntax.
async function delete() {
try {
const urls = [
[ prodLineGetURL, prodLineDeleteURL ],
[ prodGetURL, prodDeleteURL ]
];
for (const [getURL, deleteURL] of urls) {
await deleteHelper(getURL, deleteURL);
}
} catch (error) {
// handle error
}
}
One other thing that you could improve in your code is to use Promise.all instead of forEach() method to make delete requests, above code uses Promise.all inside deleteHelper function.
Your code (and all other answers) are executing delete requests sequentially, which is huge waste of time. You should use Promise.all() and execute in parallel...
// Delete Product Lines
axios.get('https://myapi.com/ProductLine?select=id')
.then(function (response) {
const ids = response.data.value
// execute all delete requests in parallel
Promise.all(
ids.map(id => axios.delete('https://myapi.com/ProductLine/' + id))
).then(
// all delete request are finished
);
})
.catch(function (error) {
})
All HTTP request are asynchronous but you can make it sync-like. How? Using async-await
Suppose you have a function called retrieveProducts, you need to make that function async and then await for the response to keep processing.
Leaving it to:
const retrieveProducts = async () => {
// Delete Product Lines
const response = await axios.get('https://myapi.com/ProductLine?select=id')
const ids = response.data.value
ids.forEach(id => {
axios.delete('https://myapi.com/ProductLine/' + id)
})
// Delete Products (I want to ensure this runs after the above code)
const otherResponse = await axios.get('https://myapi.com/Product?select=id') // use proper var name
const otherIds = response.data.value //same here
otherIds.forEach(id => {
axios.delete('https://myapi.com/Product/' + id)
})
}
But just keep in mind that it's not synchronous, it keeps being async
In Node.js, I have a Promise.all(array) resolution with a resulting value that I need to combine with the results of another asynchronous function call. I am having problems getting the results of this second function, since it resolves later than the promise.all. I could add it to the Promise.all, but it would ruin my algorithm. Is there a way to get these values outside of their resolutions so I can modify them statically? Can I create a container that waits for their results?
To be more specific, I am reading from a Firebase realtime database that has been polling API data. I need to run an algorithm on this data and store it in a MongoDB archive. But the archive opens aynchronously and I can't get it to open before my results resolve (which need to be written).
Example:
module.exports = {
news: async function getNews() {
try {
const response = await axios.get('https://cryptopanic.com/api/posts/?auth_token=518dacbc2f54788fcbd9e182521851725a09b4fa&public=true');
//console.log(response.data.results);
var news = [];
response.data.results.forEach((results) => {
news.push(results.title);
news.push(results.published_at);
news.push(results.url);
});
console.log(news);
return news;
} catch (error) {
console.error(error);
}
},
coins: async function resolution() {
await Promise.all(firebasePromise).then((values) => {
//code
return value
}
}
I have tried the first solution, and it works for the first entry, but I may be writing my async function wrong on my second export, because it returns undefined.
You can return a Promise from getNews
module.exports = {
news: function getNews() {
return axios.get('https://cryptopanic.com/api/posts/?auth_token=518dacbc2f54788fcbd9e182521851725a09b4fa&public=true')
.then(res => {
// Do your stuff
return res;
})
}
}
and then
let promiseSlowest = news();
let promiseOther1 = willResolveSoon1();
let promiseOther2 = willResolveSoon2();
let promiseOther3 = willResolveSoon3();
Promise.all([ promiseOther1, promiseOther2, promiseOther3 ]).then([data1,
data2, data3] => {
promiseSlowest.then(lastData => {
// data1, data2, data3, lastData all will be defined here
})
})
The benefit here is all promises will start and run concurrently so your total waiting time will be equal to the time taken by the promiseSlowest.
Check the link for more:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function#Examples