Rewrite "rethrow" with async/await
Below you can find the "rethrow" example. Rewrite it using async/await instead of .then/catch.
And get rid of the recursion in favour of a loop in demoGithubUser: with async/await that becomes easy to do.
class HttpError extends Error {
constructor(response) {
super(`${response.status} for ${response.url}`);
this.name = 'HttpError';
this.response = response;
}
}
function loadJson(url) {
return fetch(url)
.then(response => {
if (response.status == 200) {
return response.json();
} else {
throw new HttpError(response);
}
});
}
// Ask for a user name until github returns a valid user
function demoGithubUser() {
let name = prompt("Enter a name?", "iliakan");
return loadJson(`https://api.github.com/users/${name}`)
.then(user => {
alert(`Full name: ${user.name}.`);
return user;
})
.catch(err => {
if (err instanceof HttpError && err.response.status == 404) {
alert("No such user, please reenter.");
return demoGithubUser();
} else {
throw err;
}
});
}
demoGithubUser();There are no tricks here. Just replace .catch with try..catch inside demoGithubUser and add async/await where needed:
class HttpError extends Error {
constructor(response) {
super(`${response.status} for ${response.url}`);
this.name = 'HttpError';
this.response = response;
}
}
async function loadJson(url) {
let response = await fetch(url);
if (response.status == 200) {
return response.json();
} else {
throw new HttpError(response);
}
}
// Ask for a user name until github returns a valid user
async function demoGithubUser() {
let user;
while(true) {
let name = prompt("Enter a name?", "iliakan");
try {
user = await loadJson(`https://api.github.com/users/${name}`);
break; // no error, exit loop
} catch(err) {
if (err instanceof HttpError && err.response.status == 404) {
// loop continues after the alert
alert("No such user, please reenter.");
} else {
// unknown error, rethrow
throw err;
}
}
}
alert(`Full name: ${user.name}.`);
return user;
}
demoGithubUser();