Hello I have this async function which retrieves user profile and repositories through github api and returns them in an object.
And I want to convert this to a promise based function by using promise chaining (without any helper methods).
async function getUser(user) {
const profileResponse = await fetch(`https://api.github.com/users/${user}`);
const profileData = await profileResponse.json();
const repoResponse = await fetch(`https://api.github.com/users/${user}/repos`);
const reposData = await repoResponse.json();
// returning an object with profile and data
return {
profile:profileData,
repos:repoData,
};
}
//Calling the function here.
getUser("abufattah").then((res) => console.log(res));
I have managed to get it done using two helper functions and promise.all() method.
But how can I achieve the same thing by using promise chaining without any helper functions.
//Helper function 1: returns a promise with user profile data.
function getUserProfile(user) {
return fetch(`https://api.github.com/users/${user}`)
.then((res) =>res.json());
}
//Helper function 2: returns a promise with user repositories data.
function getUserRepos(user) {
return fetch(`https://api.github.com/users/${user}/repos?per_page=5&sort=created`)
.then((res) => res.json());
}
//Main function
function getUserWithPromise(user) {
return new Promise((resolve) => {
let profile = getUserProfile(user);
let repos = getUserRepos(user);
Promise.all([profile, repos]).then((values) => {
resolve({ profile: values[0], repos: values[1] });
});
});
}
// calling the function here
getUserWithPromise("abufattah").then((res) => console.log(res));
You can:
//Main function
function getUserWithPromise(user) {
return Promise.all([
fetch(`https://api.github.com/users/${user}`).then((res) =>res.json()),
fetch(`https://api.github.com/users/${user}/repos?per_page=5&sort=created`).then((res) => res.json())
]).then(([result1, result2]) => ({ profile: result1, repos: result2 }));
}
// calling the function here
getUserWithPromise("abufattah").then((res) => console.log(res));
Chain:
function getUserWithPromise(user) {
return fetch(`https://api.github.com/users/${user}`)
.then((res) => {
return fetch(`https://api.github.com/users/${user}/repos?per_page=5&sort=created`).then((fetch2Result) => ([res.json(), fetch2Result.json()]))
}).then(([result1, result2]) => ({ profile: result1, repos: result2 }))
}
// calling the function here
getUserWithPromise("abufattah").then((res) => console.log(res));
Transformation of async/await syntax to .then() calls is quite mechanical, especially if it doesn't involve any control flow syntax (loops or conditionals):
function getUser(user) {
return fetch(`https://api.github.com/users/${user}`).then(profileResponse => {
return profileResponse.json().then(profileData => {
return fetch(`https://api.github.com/users/${user}/repos`).then(repoResponse => {
return repoResponse.json().then(reposData => {
// returning an object with profile and data
return {
profile:profileData,
repos:repoData,
};
});
});
});
});
}
But there's no good reason to write code like that. If it's just that your target environment does not support async/await, let a transpiler do the transformation.