Sequentially Executing Promises Inside A For Loop

I am straggling with chaining two promises inside a loop, so that promise number two, does not start until promise one has been resolved. I saw an example with reduce. Could not ge

Solution 1:

Simply avoid for loops for asynchronous work.

Arrays have functional methods like forEach and map for this kind of thing.

var pendingResults = dummyData.accounts.map(function (account) {
    returncreateUser(api, {
        email: account.email,
        password: 'abc123',
        connection: 'Username-Password-Authentication'
    }).then(function (authInfo) {
        console.log("account: ", authInfo);
        returncreate(accountsAPIService, authInfo);
    });
});

Promise.all(pendingResults).then(function (results) {
    // everything is done
});

Solution 2:

See @Tomalak's answer for the actual solution.

---

The problem is that a for clause does not create a new scope for the variables. In other words, you code is understood as:

var i, cursorUser, auth0User;
for (i = 0; i < dummyData.accounts.length; i++) {
  cursorUser = dummyData.accounts[i];
  auth0User = {
    // ...
  };
  // ...
}

When the async promise is resolved, another iteration probably has already overwritten the cursorUser variable: the then callback cannot read the value of the iteration that started its promise anymore.