Question

我得到了一个＆＃34;避免嵌套承诺＆＃34; （对于jslint）用于以下函数。如何在没有嵌套承诺的情况下写出来？

function deleteUIDsFromDBForKey(rootkey, users_uids) {
  return retrieveUIDsFromDBForKey(rootkey)
    .then(uids => {
      let diff = uids.diff(users_uids)
      let deletes = []
      diff.forEach(key => {
        deletes.push(firebase.database().ref(rootkey + "/" + key).remove())
      })
      return Promise.all(deletes)
        .then(value => {
          return diff
        })
    })
}

Answer 1

在这种情况下，我认为jsLint只是指导你做错了更复杂的代码。有时，你从linter得到它，在这种情况下最好的选择是绕过特定代码或函数行或特定的linter规则的linter。

这是我能想到的最简单，最清晰的代码实现（应该是您的优先考虑）：

function deleteUIDsFromDBForKey(rootkey, users_uids) {
    return retrieveUIDsFromDBForKey(rootkey).then(uids => {
        const diff = uids.diff(users_uids);
        // wait for all deletes to be done, then return diff
        return Promise.all(diff.map(key => {
            return firebase.database().ref(rootkey + "/" + key).remove();
        })).then(() => diff);
    });
}

或者，使用Bluebird＆＃39; .map()，你可以这样做：

// using Bluebird's Promise.map()
function deleteUIDsFromDBForKey(rootkey, users_uids) {
    return retrieveUIDsFromDBForKey(rootkey).then(uids => {
        const diff = uids.diff(users_uids);
        // wait for all deletes to be done, then return diff
        return Promise.map(diff, key => {
            return firebase.database().ref(rootkey + "/" + key).remove();
        }).then(() => diff);
    });
}

或者，使用async / await：

async function deleteUIDsFromDBForKey(rootkey, users_uids) {
    const uids = await retrieveUIDsFromDBForKey(rootkey);
    const diff = uids.diff(users_uids);
    await Promise.all(diff.map(key => {
        return firebase.database().ref(rootkey + "/" + key).remove();
    }));
    return diff;
}

我没有安装支持ES7的jsLint，但最后一个选项应该避免嵌套警告。前两个，可能不是，但试图避免这个警告只会使代码变得更糟，所以IMO，你应该只是禁用警告。

避免嵌套承诺

1 个答案: