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Promisify a function that creates a mongoose model instance (i.e. a document), saves it to the model, and returns then returns the model

I'm trying to Promisify the following function
let Definition = mongoose.model('Definition', mySchema)
let saveDefinition = (newDefinition) => {
var newDef = new Definition(newDefinition);
newDef.save();
return Definition.find();
}
to achieve the following sequence of events
let saveDefinition = (newDefinition) => {
return = new Promise((res, rej) => {
// newDef = new Definition(newDefinition)
// then
// newDef.save()
// then
// return Definition.find()
})
}
The goal is to invoke this function upon a request from the client, save a document to the model called "Definition" and return all of the documents within the model back to to the client. Any help or guidance would be greatly appreciated.
I'm not really sure on how to approach the problem

a function that creates a mongoose model instance (i.e. a document), saves it to the model, and returns then returns the model
There is nothing special you need to do. .save() already returns (a promise for) the saved document. Return it.
const Definition = mongoose.model('Definition', mySchema);
const saveDefinition = (data) => {
const newDef = new Definition(data);
return newDef.save();
};
Done.
I would write it differently to get rid of that global Definition variable:
const saveObject = modelName => {
const Model = mongoose.model(modelName, mySchema);
return (data) => new Model(data).save();
};
const saveDefinition = saveObject('Definition');
const saveWhatever = saveObject('Whatever');
Usage is the same in both cases
saveDefinition({ /* ... */ }).then(def => {
// success
}).catch(err => {
// failure
});
or
async () => {
try {
const def = await saveDefinition({ /* ... */ });
// success
} catch (err) {
// failure
}
};

How can I insert objects in SQL Server running a function in a loop? ConnectionError: .connect can not be called on a Connection in `Connecting` state

I'm working in a NodeJS project, this project I decided to change the way I'm doing it because this way wasn't working, let me try to explain it.
I need to insert data into a SQL Server DB, so I did a function insertOffice() this function opens a connection using Tedious, then fetchs data to an url with data from an array data2 to load coords, and then with this coords creates an object, then inserts this object into a DB. When inserting only one part of my data2 array, it works, by only sendind data[0] it adds:
{
latjson: 1,
lonjson: 1,
idoficina: "1",
}
But I want to insert both of the parts of my array, changing data2[0] to data2[index], to be able to insert all my array, so I tried creating another function functionLooper()that loops insertOffice() to insert my data from my array data2.
I builded this little code to learn how to loop a function, this prints index that is the value I use for bringing idoficina.
As you can see functionLooper() runs the code twice, so it can read fully data2 array, I have this little code that works with the same logic, I builded my full code using this:
function insertOffice(index) {
console.log(index);
}
function functionLooper() {
for (let i = 0; i < 5; i++) {
let response = insertOffice(i);
}
}
functionLooper();
This prints:
0
1
2
3
4
So my code it's supposed to send index
I'm expecting my code to loop my insertOffice() and being able to insert my objects, the issue is that this doesn't seems to work as I am getting this error:
C:\...\node_modules\tedious\lib\connection.js:993
throw new _errors.ConnectionError('`.connect` can not be called on a Connection in `' + this.state.name + '` state.');
^
ConnectionError: `.connect` can not be called on a Connection in `Connecting` state.
this is my code:
var config = {
....
};
const data2 = [
...
];
var connection = new Connection(config);
function insertOffice(index) {
console.log(index)
connection.on("connect", function (err) {
console.log("Successful connection");
});
connection.connect();
const request = new Request(
"EXEC SPInsert #Data1, ... ",
function (err) {
if (err) {
console.log("Couldn't insert, " + err);
} else {
console.log("Inserted")
}
}
);
console.log(myObject.Id_Oficina)
request.addParameter("Data1", TYPES.SmallInt, myObject.Id_Oficina);
request.on("row", function (columns) {
columns.forEach(function (column) {
if (column.value === null) {
console.log("NULL");
} else {
console.log("Product id of inserted item is " + column.value);
}
});
});
request.on("requestCompleted", function () {
connection.close();
});
connection.execSql(request);
}
function functionLooper() {
for (let i = 0; i < 2; i++) {
let response = insertOffice(i);
}
}
functionLooper();
I do not know if this is the right way to do it (looping the inserting function insertOffice()twice), if you know a better way to do it and if you could show me how in an example using a similar code to mine, would really appreciate it.

You're approaching an asynchronous problem as if it's a synchronous one. You're also making your life a bit harder by mixing event based async tasks with promise based ones.
For example, connection.connect() is asynchronous (meaning that it doesn't finish all its work before the next lines of code is executed), it is only done when connection emits the connect event. So the trigger for starting the processing of your data should not be started until this event is fired.
For each of the events in your loop they are not running one at a time but all at the same time because the fetch() is a promise (asynchronous) it doesn't complete before the next iteration of the loop. In some cases it may have even finished before the database connection is ready, meaning the code execution has moved on to DB requests before the connection to the database is established.
To allow your code to be as manageable as possible you should aim to "promisify" the connection / requests so that you can then write an entirely promise based program, rather than mixing promises and events (which will be pretty tricky to manage - but is possible).
For example:
const connection = new Connection(config);
// turn the connection event into a promise
function connect() {
return new Promise((resolve, reject) => {
connection.once('connect', (err) => err ? reject(err) : resolve(connection));
connection.connect()
});
}
// insert your data once the connection is ready and then close it when all the work is done
function insertOffices() {
connect().then((conn) => {
// connection is ready I can do what I want
// NB: Make sure you return a promise here otherwise the connection.close() call will fire before it's done
}).then(() => {
connection.close();
});
}
The same approach can be taken to "promisify" the inserts.
// turn a DB request into a promise
function request(conn) {
return new Promise((resolve, reject) => {
const request = new Request(...);
request.once('error', reject);
request.once('requestCompleted', resolve);
conn.execSql(request);
});
}
This can then be combined to perform a loop where it's executed one at a time:
function doInserts() {
return connect().then((conn) => {
// create a "chain" of promises that execute one after the other
let inserts = Promise.resolve();
for (let i = 0; i < limit; i++) {
inserts = inserts.then(() => request(conn));
}
return inserts;
}).then(() => connection.close())
}
or in parallel:
function doInserts() {
return connect().then((conn) => {
// create an array of promises that all execute independently
// NB - this probably won't work currently because it would need
// multiple connections to work (rather than one)
let inserts = [];
for (let i = 0; i < limit; i++) {
inserts.push(request(conn));
}
return Promise.all(inserts);
}).then(() => connection.close())
}

Finally I could fix it, I'm sharing my code for everyone to could use it and do multiple inserts, thanks to Dan Hensby, I didn't do it his way but used part of what he said, thanks to RbarryYoung and MichaelSun90 who told me how, just what I did was changing my
var connection = new Connection(config);
to run inside my
function insertOffice(index) { ... }
Looking like this:
function insertOffice(index) {
var connection = new Connection(config);
....
}

How do I log responses in the correct order using Async code

I need to create a function that runs a 'getFile' function on each item in an array. The getFile function logs 'File contents of x' x being whatever element is in the array.
Currently, I have a working function that runs the getFile on the array and waits for the final response before logging the results.
However, I now need to log the responses as I receive them in order. For example, if my array is [1, 2, 3, 4, 5] currently it logs 'File contents of x' in a random order, so if it was to return the logs, 3 then 4 then 1. As soon as I receive 1, I need to log that, then once I receive 2 logs that and so on.
I will insert my current code below. The problem I'm having is I need to know when the 'empty space' in my array becomes populated so I can log it in real time. Therefore allowing my user to see the result build up rather than just having to wait until all the responses have come back
function fetchContentOfFiles(fileNames, testCB) {
const fileContent = [];
let counter = 0;
fileNames.forEach((file, i) => {
getFile(file, (err, fileName) => {
if (err) console.log(err)
else {
fileContent[i] = fileName;
counter++
if (counter === fileNames.length) {
testCB(null, fileContent)
};
console.log(fileContent)
};
});
});
};

The cleanest way to write this would be to use a for loop inside an async function. Promisify getFile so that it returns a Promise, then await it in every iteration of the loop. At the end of the loop, call the callback:
const getFileProm = file => new Promise((resolve, reject) => {
getFile(file, (err, fileName) => {
if (err) reject(err);
else resolve(fileName);
});
});
async function fetchContentOfFiles(fileNames, testCB) {
const fileContent = [];
try {
for (let i = 0; i < fileNames.length; i++) {
fileContent.push(
await getFileProm(fileNames[i])
);
}
} catch(e) {
// handle errors, if you want, maybe call testCB with an error and return?
}
testCB(null, fileContent);
}
It would probably be even better if fetchContentOfFiles was called and handled as a Promise rather than with callbacks, and then the errors can be handled in the consumer:
async function fetchContentOfFiles(fileNames) {
const fileContent = [];
for (let i = 0; i < fileNames.length; i++) {
fileContent.push(
await getFileProm(fileNames[i])
);
}
return fileContent;
}
fetchContentOfFiles(arr)
.then((fileContent) => {
// do stuff with fileContent
})
.catch((err) => {
// something went wrong
});

Wait for mongo writes before returning from a find

I want a store js object that manages a mongodb collection and behaves like that:
store.insert(thing); // called from a pubsub system that don't wait the insert to finish
store.get(); // returns a promise that resolves to the things in the collection
// even if called immediately after insert it must contain the last thing inserted
I implemented it manually like that:
let inserts = 0;
let afterInserts = [];
const checkInsertsFinished = () => {
if (inserts === 0) {
afterInserts.forEach(resolve => resolve());
afterInserts = [];
}
};
const decrementInserts = () => {
inserts -= 1;
checkInsertsFinished();
};
const insertsFinished = () =>
new Promise((resolve) => {
afterInserts.push(resolve);
checkInsertsFinished();
});
const insert = (thing) => {
inserts += 1;
db.collection('mycollection').insertOne(thing).then(decrementInserts);
};
const get = async () => {
await insertsFinished(); // if there are inserts happening, wait for them to finish
return db.collection('mycollection').find({}).toArray();
};
return { insert, get };
I suppose that there are more standard ways to accomplish this but I miss the vocabulary to find libs or built-in features... How would you do that?
Thanks for your advices.

JavaScript is single threaded, none of code you write can be run at the same time on multiple threads so you should be able to do it this way:
let inserting = Promise.resolve(),
startGetting={};
const insert = (thing) => {
startGetting={};//de-reference startGetting
inserting = db.collection('mycollection').insertOne(thing)
return inserting;
};
const get = () => {
const rec = () =>
inserting.then(
_ =>
new Promise(
(resolve,reject)=>{
//the next op is truely async (although I wonder why no promise),
// someone can insert while this is completing
const start=startGetting;
db.collection('mycollection').find({}).toArray(
(err,results)=>
err
? reject(err)
//inserting could have been set to tby the time
// this completed (in theory) so use startGetting reference equality
: startGetting === start
? resolve(results)//while getting nobody inserted
: resolve(rec())
)
})
);
return rec();
};
return { insert, get };

sequential call using promise inside loop

i want to perform synchronous operation of functions using promise. I have loop that passes the data to be inserted to insert function and after inserting one row i want to check the no. of rows exists in table hence i am performing select operation.
But the issue is if there are 3 records then it inserts all 3 records and after that my select function gets executed. what i want is after insertion of one record select function gets called.
here is my pseudo code as entire code involves lot of operations
for(var i=0; data.length ; i++){
self.executeFeedbackTrack(data);
}
executeFeedbackTrack:function(callInfo){
var self=this;
return self.insertFeedbackTrack(callInfo).then(function(data){
console.log("insertFeedbackTrack status "+status);
return self.getFeedbackTrack();
});
},
getFeedbackTrack :function(){
return new Promise(function(resolve,reject){
var objDBFeedbackTrack = new DBFeedbackTrack();
objDBFeedbackTrack.selectFeedbackTrack(function(arrayCallRegisters){
if(arrayCallRegisters){
console.log("notification.js no. of feedbacks "+arrayCallRegisters.length);
resolve(arrayCallRegisters.length);
}
});
});
},
insertFeedbackTrack :function(callInfo){
return new Promise(function(resolve,reject){
var objDBFeedbackTrack = new DBFeedbackTrack();
objDBFeedbackTrack.insertFeedbackTrack(callInfo.callNumber,callInfo.callServiceType,function(status){
resolve(status);
$('#loader').hide();
});
});
}

The previous answer is good, but if you are using nodejs, or babel, or you are using only modern browsers. You can use an async-await pair, it is es8 stuff.
let insertFeedbackTrack = function(){ return new Promise(/***/)};
let getFeedbackTrack = function(){ return new Promise(/***/)};
let processResult = async function(data){
let feedbacks = [];
for(let i=0;i<data.length;i++){
let insertedResult = await insertFeedbackTrack(data[i]);//perhaps you will return an id;
let feedbackTrack = await getFeedbackTrack(insertedResult.id);
feedbacks.push(feedbackTrack);
}
return feedbacks;
}
processResult(data).then(/** do stuff */)

It looks to me like this is caused by executing a series of asynchronous inserts, and assuming that the get of insert n (inside of a .then()) is called before insert n+1 is executed. However, I'm not aware of any such guarantee, in JavaScript; all that I'm familiar with is that then n will be called after insert n, not that it would be called before insert n+1.
What I'd suggest is avoiding this mix of traditional and callback-based code, and instead put the iteration step inside getFeedbackTrack().then. Assuming this understanding of the issue is correct, then something like the following should work:
function iterate(i) {
if (i < data.length) {
obj.insertFeedbackTrack(data[i]).then(function(insertResult) {
self.getFeedbackTrack().then(function(getResult) {
// this line is the important one, replacing the `for` loop earlier
iterate(i+1);
});
});
}
}
iterate(0);
By doing that, you would guarantee that insert for the next element does not occur until the current select executes successfully.
Naturally, you may also want to restructure that to use chained .then instead of nested; I used nested rather than chained to emphasize the ordering of callbacks.

This can be solved by using a very handy JS library Ramda. Concept is to use two methods, one is R.partial and another is R.pipeP.
First create a promises array from your data array, like following.
var promises = data.map(function(i) {
return R.partial(sample, [i])
});
Then you can pass this promise to R.pipeP, so that it can be executed one after another. like below.
var doOperation = R.pipeP.apply(this, promises)
Please execute following snippet attached.
// Sample promise returning function
function sample(d) {
return new Promise(function(resolve, reject){
setTimeout(function() {
console.log('resolved for:' + d);
resolve(d);
}, 1000)
})
}
// Sample data
var data = [1, 2, 3, 4, 5]
// Converting data array to promise array
var promises = data.map(function(i) {
return R.partial(sample, [i])
});
var doOperation = R.pipeP.apply(this, promises)
doOperation();
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.min.js"></script>
So in your case, the code will look like this
var promises = data.map(function(i) {
return R.partial(self.executeFeedbackTrack, [i])
});
var doOperation = R.pipeP.apply(this, promises)
doOperation();

I use yield for such cases if using generator functions.
for(var i = 0; i < order.tasks.length; i++){
if(order.tasks[i].customer_id === 0){
var name = order.tasks[i].customer_name.split(" ")
const customers = yield db.queryAsync(
`INSERT INTO customers(
business_id)
VALUES(?)
`,[order.business_id])
}
}
Or else I use self-calling functions in case of callbacks.
var i = 0;
(function loop() {
if (i < data.length) {
task_ids1.push([order.tasks[i].task_id])
i++;
loop();
}
}());

Here's how I would sequentially call promises in a loop (I'm using ES7).
First, let's define some basic data:
const data = [0,1,2,3];
Then, let's simulate some long running process, so let's create a function that returns a Promise (you can think of this as a simulated network request, or whatever suits your needs)
const promiseExample = (item) =>
new Promise((res) => {
setTimeout(() => {
console.log('resolved ', item);
res(item);
}, 1000);
});
Now, let's create an array of promises. What the next line of code does is: for every item in the array data, return a promise factory. A promise factory is a function that wraps a certain promise without running it.
const funcs = data.map(item => async () => await promiseExample(item));
Now, the actual code starts here. We need a function that does the actual serialization. Since it has to handle an array of promiseFactories, I split it in two functions, one for the serialization of a single promise, and one for handling an array of promiseFactories.
const serializePromise = promiseFactoryList =>
promiseFactoryList.reduce(serialize, Promise.resolve([]));
const serialize = async (promise, promiseFactory) => {
const promiseResult = await promise;
const res = await promiseFactory();
return [...promiseResult, res];
};
Now, you can simply call it like this:
serializePromise(funcs).then(res => {
console.log('res', res);
});
As you can see, the code is pretty simple, elegant, functional, and doesn't need any external dependency. I hope this answers your question and helps you!
const serializePromise = promiseFactoryList =>
promiseFactoryList.reduce(serialize, Promise.resolve([]));
const serialize = async (promise, promiseFactory) => {
const promiseResult = await promise;
const res = await promiseFactory();
return [...promiseResult, res];
};
const data = [0,1,2,3];
const promiseExample = (item) =>
new Promise((res) => {
setTimeout(() => {
console.log('resolved ', item);
res(item);
}, 1000);
});
const funcs = data.map(item => async () => await promiseExample(item))
serializePromise(funcs).then(res => {
console.log('res', res);
});

I ran into this problem recently and solved it as shown below. This is very similar to the answer by #Ethan Kaminsky, but only uses callbacks. This may be useful for people avoiding promises for whatever reason.
In my application the asynchronous function may fail and can safely be retried; I included this logic because it's useful and doesn't overly complicate the routine, but it is not exercised in the example.
// Some callback when the task is complete
function cb(...rest) { window.alert( `${rest.join(', ')}` ) }
// The data and the function operating on the data
// The function calls "callback(err)" on completion
const data = [ 'dataset1', 'dataset2', 'dataset3' ]
const doTheThing = (thingDone) => setTimeout( thingDone, 1000 )
let i = -1 // counter/interator for data[]
let retries = 20 // everything fails; total retry #
// The do-async-synchronously (with max retries) loop
function next( err ) {
if( err ) {
if( ! --retries ) return cb( 'too many retries' )
} else if( ! data[++i] ) return cb( undefined, 'done-data' )
console.log( 'i is', i, data[i] )
doTheThing( next, data[i] ) // callback is first here
}
// start the process
next()