javascript - 仅当 Promise 解析时才使用 JS Array.push

Question

我有以下功能:

installationService.getInstallationMail = (id) => {
  return cloudant.readDocument(dbInstallations, id)
    .then(installation => {
      return installation.supportMail;
    });
};

然后我有一个函数，其中有以下 forEach 循环:

properties.forEach(item => {
  if ((item.value > 0) && ((dateNow - item.value) > dateOneDay)) {
    let index = item._id.lastIndexOf("_");
    let result = item._id.substr(0, index);
    item["baseId"] = result;

    let email = installationService.getInstallationMail(item.baseId);
    item["supportMail"] = email;

    notifications.push(item);
  }
});
console.log(notifications);

console.log 通知返回给我:

[ { _id: 'id_9oW9i8M9RU_CbT1mKOGPG',
    _rev: '26129-6dd842ab825bf291d876486b8157b07b',
    control: false,
    dataType: 1,
    maxValue: '100',
    measurable: true,
    minValue: '0',
    parentId: 'id_9oW9i8M9RU_eFyeP6BmdI',
    precision: 2,
    propertyType: 7,
    value: '1522907022112',
    baseId: 'id_9oW9i8M9RU',
    supportMail: Promise { <pending> } } ]

我现在的问题是，当 Promised 得到解决时，如何在 forEach 循环中推送项目(包括电子邮件)？

我尝试过

Promise.all(email).then(item => {
  item["supportMail"] = email; 
  notifications.push(item);
});

相反，但这也不起作用。

这里重要的是，我想在 forEach 循环之外访问通知。如果我将 forEach 更改为异步函数，则 notifications 的 console.log 将在循环之前运行。

这是整个 JavaScript 供引用:https://jsbin.com/gujiwatati/edit?js

Answer 1

const notifications = [];
installationService.getInstallationMail = (id) => {
    return cloudant.readDocument(dbInstallations, id)
        .then(installation => {
            return installation.supportMail;
        });
};
Promise.all(properties.map((item) => {
    if ((item.value > 0) && ((dateNow - item.value) > dateOneDay)) {
        let index = item._id.lastIndexOf("_");
        let result = item._id.substr(0, index);
        item["baseId"] = result;
        let email = installationService.getInstallationMail(item.baseId);
        email.then((email) => {
            // update item after email resolves
            item["supportMail"] = email; 
        });
        notifications.push(item);
        // returm email Promise
        return email;
    }
})).then(() => { // wait for all pending email Promise's to finish
    console.log(notifications);
});

您还可以使用await/async语法

await Promise.all(properties.map(async (item) => {
    if ((item.value > 0) && ((dateNow - item.value) > dateOneDay)) {
        let index = item._id.lastIndexOf("_");
        let result = item._id.substr(0, index);
        item["baseId"] = result;
        let email = await installationService.getInstallationMail(item.baseId);
        item["supportMail"] = email;
        notifications.push(item);
    }
}));