JS Array.push only when Promise resolved

Question

I have the following function:

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

Then I have a function in which I have the following forEach loop:

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 for notifications returns me:

[ { _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> } } ]

My question is now how I can push the items (including the email) in my forEach loop when the Promised is resolved?

I tried it with

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

instead but this also did not work.

The important thing here is, that I want to access notifications outside the forEach loop. If I change the forEach to a async function, the console.log for notifications runs before the loop.

This is the whole JavaScript for reference: https://jsbin.com/gujiwatati/edit?js

ponury-kostek · Accepted Answer · 2018-11-06 14:28:37Z

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);
});

You can also use await/async syntax

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);
    }
}));

Juanín · Accepted Answer · 2018-11-06 14:02:13Z

0

What your function installationService.getInstallationMail is returning is not a string as you might be expecting, what you are receiving is a promise cloudant.readDocument is returning. I suggest you to do something like the following:

installationService.getInstallationMail = (id) => {
  let promise = Promise();
  cloudant.readDocument(dbInstallations, id)
    .then(installation => {
      promise.resolve(installation.supportMail);
      return;
    });
  return promise;
};
let emailPromise = installationService.getInstallationMail(item.baseId);
emailPromise.then(email => {
  item["supportMail"] = email;
  notifications.push(item);
  console.log(item);
})

answered Nov 6, 2018 at 14:02

Juanín

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