Riscrivere "rethrow" con async/await
Sotto puoi trovare l’esempio “rethrow”. Riscriverlo usando async/await invece di .then/catch.
Sbarazzarsi della ricorsione a favore di un ciclo in demoGithubUser: con async/await diventa facile da fare.
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: ${user.name}.`); return user; }) .catch(err => { if (err instanceof HttpError && err.response.status == 404) { alert("No such user, please reenter."); return demoGithubUser(); } else { throw err; } }); } demoGithubUser();Non ci sono trucchi qui. Basta sostituire .catch with try...catch dentro demoGithubUser e aggiungere async/await quando necessario:
class HttpError extends Error { constructor(response) { super(`${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();