I am having a function which does some async processing and I want to convert it to a promise, so that I can make a "chain of execution" with other depended functions later on.
Below is the code(slightly modified for privacy):
router.get('/api/prx/ptr', function(req, res) {
let prx = req.params.prx_id
let ptr = {}
let parse_text = (idx_array, prx) => {
for(let name of idx_array) {
if (typeof ptr[name] === 'undefined') {
ptr[name] = []
}
get_text(prx, name, (tg) => {
const pst = new Set(tg.ph.map(ps => ps.label))
pst.forEach(ps => {
ptr[name].push(ps)
})
})
}
return true
}
parse_text = promisify(parse_text)
documentExists(prx, function(err, dbexists){
if (err) {
console.log(err);
return res.status(404).send(err)
}
get_idx_array(prx, function(err, idx_array){
if (err) {
return res.status(err.code || 400).send(err)
}
idx_array = idx_array.map(function(v){return v._id});
parse_text(idx_array, prx)
.then(result => {
res.status(200).send(ptr)
})
})
})
})
The problem is that in the last line, the promise never resolves and thus the request-response cycle never ends. Not sure what I have done wrong in my setup. Any help appreciated.
Related
Express router is not awaiting my forEach loop and sends the old unmanipulated object as a response instead of the new manipulated data.
Here I am using Sequalize as my ORM.
router.get('/', async (req,res) => {
try {
let trainings = await db.Training.findAll();
let locations = await db.Location.findAll();
await locations.forEach(location => {
trainings.forEach(training => {
if(location.trainingId == training.id){
training["location"] = location
}
})
})
res.status(200).json({
training:trainings
})
} catch(err) {
console.log(err);
res.status(404).json({
message : err
})
}
})
Basically you are using the await keyword against a synchronous process which is
locations.forEach(location => {
trainings.forEach(training => {
if(location.trainingId == training.id){
training["location"] = location
}
})
})
These lines of code doesn't return any promise or behave like a promise. So one solution can be having a function
function modify(trainings,locations){
return new Promise((resolve,reject)=>{
locations.forEach(location => {
trainings.forEach(training => {
if(location.trainingId == training.id){
training["location"] = location
}
})
})
resolve('done')
})
}
then have it like this
let trainings = await db.Training.findAll();
let locations = await db.Location.findAll();
await modify(trainings,locations)
or you can simply remove the await keyword from your current state of code.
I have the following codes :
app.post("/login/auth", (req, res) => {
(async function() {
let NikitaBellucci = (await auth.login(req, db, crypto))[0];
res.send(NikitaBellucci);
})();
});
and
exports.login = (req, db, crypto) => {
pro = new Promise((resolve,reject) => {
let pseudo = req.body.pseudo;
let password = crypto.createHmac('sha256', req.body.password)
.update('jojofags suck')
.digest('hex');
let query = "SELECT * FROM users WHERE users.pseudo = ? AND users.password = ? LIMIT 1";
db.query(query, [pseudo, password], function (err, result) {
if (err) throw err; // GESTION D'ERREURS
result.isAdministrator = function() {
if(this.role <= 90) { return true; } else { return false; }
}
resolve(result);
});
})
return pro.then((val) => {
console.log(val);
return val;
})
}
On console.log(val);, I can see the previously added method to my object. But when returning it to my main file, method "disappear", how to avoid that?
thank you
Your function is attached to the entire result object, but you get the 0 property of it in (await auth.login(req, db, crypto))[0]; which won't have the function. Just remove the [0] and NikitaBellucci.isAdministrator will be the function in question.
I have some problems with the multiple promises in my code. There is no way to return to items who are not in the database. I changed the code multiple times but no luck. The only data it returns is "datas": [
null,
null
]
This is my code
var start = function(offset, entry) {
return new Promise(function(resolve, reject) {
rp('************' + entry).then(function(repos) {
resolve(repos);
}).catch(function(err) {
reject(err);
});
});
};
var findnewones = function(iten) {
return new Promise(function(resolve, reject) {
return Promise.all(iten.items.map(function(ndtrcitem) {
return new Promise(function(resolve, reject) {
Items.findOne({"metadata.trcid": ndtrcitem.metadata.trcid}).exec(function(err, doc) {
if (!doc) {
resolve(ndtrcitem);
}
});
})
})).then(datas => {
resolve(datas);
});
})
}
exports.find = function(req, res, next) {
var ndite = ["locations", "events"];
var items = [];
return Promise.all(ndite.map(function(entry) {
return start(0, entry).then(function(res) {
for (i = 0; i <= res.count; i += 10) {
return start(i, entry).then(function(iten) {
findnewones(iten).then(function(dat) {
items.push(dat);
});
});
}
return items;
})
})).then(datas => {
res.json({datas});
});
}
I think because the for loop there is synchronous and it's not waiting for the start() promise to resolve.
for (i = 0; i <= res.count; i += 10) {
return start(i, entry).then(function(iten) {
findnewones(iten).then(function(dat) {
items.push(dat);
});
});
}
I have replaced it with async/await, don't know if it will work right away, I am just providing you with a hint in this very complicated promise chain. If it or any variation of it works please update this answer.
exports.find = function (req, res, next) {
var ndite = ["locations", "events"];
var items = [];
return Promise.all(ndite.map(function (entry) {
return start(0, entry)
.then(async function (res) {////// this
for (i = 0; i <= res.count; i += 10) {
await start(i, entry).then(function (iten) { ////this
findnewones(iten).then(function (dat) {
items.push(dat);
});
});
}
return items;
})
})).then(datas => {
res.json({
datas
});
});
}
I'm trying to write a chain of Promises but the last .then() is being called multiple times and I don't know why. The last .then() must run a single time because it will call another API passing result as body.
I know that is being called multiple times because I'm logging as console.log().
What is wrong on my code? For my understand, then() should wait promise returns something.
app.post('/router/join', function(req, res){
let data = req.body;
sessions.validate(data)
.then(result => {
return {
authenticated: (result.code === 201)
};
})
.then(result => {
if(result.authenticated){
return contacts.getContacts(data.tenant_id).then(cs => {
let json = merge(result, cs.data);
return Promise.all(cs.data.items.map(contact => {
return messages.getLastMessage(data.tenant_id, contact.item.contact_id, data.hash_id)
.then(result => {
contact.item.last_message = result.code === 200 && result.data.length > 0 ? result.data[0] : null;
return contact;
});
})).then(result => {
json.items = result;
return json;
});
});
} else {
return result;
}
})
.then(result => {
//this call should run after all other promises and only a single time
let event = result.authenticated ? 'valid_session' : 'invalid_session';
console.log('222');
proxy.send(event, result)}
)
.catch(err => {
console.log('333');
proxy.send('invalid_session', {socket_id: data.socket_id})
})
res.status(201).send({});
});
You can use async/await to clean it up. Inside async functions you can await the results of promises.
app.post('/router/join', async function (req, res, next) {
try {
let data = req.body;
let {code} = await sessions.validate(data);
let result = { authenticated: (code === 201) };
if (result.authenticated) {
let cs = await contacts.getContacts(data.tenant_id);
let json = merge(result, cs.data);
let items = Promise.all(cs.data.items.map(async contact => {
let result = await messages.getLastMessage(data.tenant_id, contact.item.contact_id, data.hash_id)
contact.item.last_message = result.code === 200 && result.data.length > 0 ? result.data[0] : null;
return contact;
}));
json.items = items;
result = json;
}
let event = result.authenticated ? 'valid_session' : 'invalid_session';
console.log('222');
proxy.send(event, result);
res.status(201).send({});
} catch (err) {
proxy.send('invalid_session', {socket_id: data.socket_id})
next (err);
}
});
The problem is with the promises and the async function. "All moved" is supposed to be logged after everything in async.each is done. But nothing is ever logged.
Here is my exports functions:
var courier_id = data.ref.parent.key;
return admin.database().ref("firewall_queue/"+courier_id+"/orders").once('value',function(orders){
//console.log(Object.keys(orders.val()));
async.each(Object.keys(orders.val()), function (order, callback) {
if(order != "none") {
return moveToWaitingFromFirewall(order).then(callback())
}
},
function (err) {
console.log("All moved");
return admin.database().ref("/firewall_queue/"+courier_id+"/orders/").remove().then(()=>{
return pushToPending(courier_id,data.ref.key);
})
});
})
Here is my moveToWaitingFromFirewall function:
function moveToWaitingFromFirewall(order_id){
var order = {};
order.id = order_id;
var promises = [];
promises.push(new Promise((resolve) => {
admin.database().ref("orders/"+order_id+"/zone").once('value').then(function(zone){
order.zone = zone.val();
resolve();
})
}))
promises.push(new Promise((resolve) => {
admin.database().ref("orders/"+order_id+"/time_order_placed").once('value').then(function(time_order_placed){
order.time = time_order_placed.val();
resolve();
})
}))
//grab zone and time first
return Promise.all(promises).then(()=>{
return admin.database().ref(order.zone+"/wait_order_queue/"+order.id).set(order.time);
})
}
JSON Firebase
"c98" : {
"orders" : {
"0333" : 123123,
"0345" : 12,
"0911" : 123,
"none" : "none"
}
Study this a little bit, and maybe apply to your current code.
Imagine admin.database().ref("orders/"+order_id+"/time_order_placed").once('value') is like delay(time)
// let delay = time => new Promise(res=>setTimeout(res,time));
let delay = function(time){
return new Promise(function(resolve,reject){
setTimeout(function(){
resolve();
},time);
});
}
let myPromise = function(order){
return Promise.all([
delay(500),
delay(500),
delay(1000).then(function(){
console.log('Order complete: ',order);
return; // returns undefined, so cb doesn't pass anything to cb(err), but use ()=>cb() to avoid this anyways.
})
]);
}
let orders = [1,2,3];
async.each(orders,function(order,cb){
myPromise(order)
.then(()=>cb())
.catch(err=>cb(err));
},function(err,data){
if(err){
console.log('Err',err);
}else{
console.log('all Finished');
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/async/2.6.0/async.js"></script>