Now I've working on NodeJS and Sequelize to query and process an database data.
I've call findAll from Table1 and I want to query each rows to apply some data to Table2 then I want to add all data to array before send output, I did like this
var last_promise;
var output_results = {};
Table1Model.findAll()
.then(function(results1)
{
for (var i = 0; i < results1.length; ++i)
{
var result1 = results1[i];
output_results[result1.id] = result1;
var add_promise = Table2Model
.create({
id_from_table1: result1.id,
data_from_table1: result1.data
});
.then(function(result2) {
output_results[result2.id_from_table1].data2 = result2;
});
if (last_promise)
{
last_promise.then(function()
{
return add_promise;
});
} else {
last_promise = add_promise;
}
}
}
}
last_promise.then(function() {
return output_results;
}
I want to know that there any better way to execute promises sequentially in a loop like this ?
It looks like you can do that with .all() method:
Table1Model
.findAll()
.then(function(results1) {
return Promise.all(results1.map(function(result) {
return Table2Model
.create({
id_from_table1: result1.id,
data_from_table1: result1.data
})
.then(function(result2) {
...
});
}));
})
.then(function(output_results) {
});
Related
I'm little bit confusing in promises. first, I have some ugly code like this:
async function presence(ctx) {
try {
var prsenceData = [];
var isSuccess = Boolean(false);
var ckFilePath = "./somepath/cookie.json";
if (!fs.existsSync(ckFilePath)) {
await menuLogin.login(ctx).then(login => {
isSuccess = Boolean(login[0].status);
myCk.saveCookies(login[0].cookies, ckFilePath);
if (!isSuccess) {
myCk.deleteCookies(ckFilePath);
return false;
}
});
} else {
await myCk.checkToDelete(ckFilePath).then(isDel => {
if (isDel) {
return false;
}
});
}
await presenceNow.check(fs.existsSync(ckFilePath), ctx).then(data => {
for (let id = 0; id < data[0].pesan.length; id++) {
console.log(data[0].pesan[id]);
}
for (let id = 0; id < data[0].id.length; id++) {
presenceData.push(data[0].id);
}
if (data[0].pesan.length == 0 && fs.existsSync(ckFilePath)) {
myCk.deleteCookies(ckFilePath);
}
});
} catch (e) {
console.log(e);
}
return presenceData;
}
Can anyone explain why presenceNow.check() function is not calling if my ckFilePath does not exist? but if myCkFilePath is exist, my code run so well. And maybe anyone can show me the better code for that case? thanks.
Mixing async/await and promise chains like this is something of a code smell that the author lacked an understand of async/await. It's also something of a mixed metaphor.
If you refactor it to actually use async/await you get something like this that's a lot easier to understand.
My suspicion is that your presenceNow.check() method is not being called because the function is taking returning via one of the two return paths above it:
the file exists and myCk.checkToDelete() returns true, or
the file does not exist, and the login is unsuccessful.
const fs = require('fs/promises');
async function presence(ctx) {
var presenceData = [];
var isSuccess = false;
var ckFilePath = "./somepath/cookie.json";
let ckFilePathExists = await fs.access(ckFilePath);
if (ckFilePathExists) {
const isDel = await myCk.checkToDelete(ckFilePath);
if (isDel) {
return false;
}
} else {
const login = await menuLogin.login(ctx);
const isSuccess = login[0].status
myCk.saveCookies(login[0].cookies, ckFilePath);
if (!isSuccess) {
myCk.deleteCookies(ckFilePath);
return false;
}
}
ckFilePathExists = await fs.access(ckFilePath)
const data = await presenceNow.check(ckFilePathExists, ctx);
for (let id = 0; id < data[0].pesan.length; id++) {
console.log(data[0].pesan[id]);
}
for (let id = 0; id < data[0].id.length; id++) {
presenceData.push(data[0].id);
}
if (data[0].pesan.length == 0 && await fs.access(ckFilePath) ) {
myCk.deleteCookies(ckFilePath);
}
return presenceData;
}
I have an API in NestJs which is not sending data on the first hit. However, on hitting it again it sends the desired data. I am guessing the API returns before the internal processing is done.
How to stop this. Is sleep a good option for this?
Or is there any other way to do this?
#Post("load")
#UseGuards(AuthGuard("jwt"))
async load(#Req() body: any)
{
const organizationId = body.user.organizationId;
const userId = body.user.userId;
if ("brandIds" in body.body)
{
await this.userService.onBoardUser(userId);
}
var settings = await this.settingsService.fetchLayout(organizationId, "home");
settings.forEach(async (element) =>
{
var parsedElement = JSON.parse(JSON.stringify(element));
var innerContent = await this.fetchContent(parsedElement.method, organizationId, userId);
var template = parsedElement.content[0];
let formattedItem = {};
innerContent.forEach((item) =>
{
try
{
formattedItem = template;
Object.keys(template).forEach((key) =>
{
if (template[key]!= "" && key != "type")
{
formattedItem[key] = eval(template[key]);
}
});
parsedElement.content.push(formattedItem);
formattedItem = null;
}
catch(err)
{
}
});
this.response.data.push(parsedElement);
innerContent = null;
template = null;
formattedItem = null;
parsedElement = null;
});
return(this.response);
}
looks like your main problem here is that your using async/await inside foreach which isnt working.
Use it like this:
for (const setting of settings) {
... your async code here.
}
It is 2016, Node has had nearly full ES6 support since v4, and Promises have been around since 0.12. It's time to leave callbacks in the dust IMO.
I'm working on a commander.js-based CLI util which leverages a lot of async operations - http requests and user input. I want to wrap the Commander actions in async functions so that they can be treated as promises, and also to support generators (useful for the co-prompt library I'm using for user input).
I've tried wrapping the CB with co in two ways:
1)
program.command('myCmd')
.action(program => co(function* (program) {...})
.catch(err => console.log(err.stack)) );
and
2) program.command('myCmd').action(co.wrap(function* (program) { .. }));
The problem with 1) is that the program parameter isn't passed
The problem with 2) is that errors are swallowed...
I'd really like to get this working as it yields much nicer code in my use case - involving a lot of http requests and also waiting for user input using the co-prompt library..
Is it a better option altogether perhaps to wrap program.Command.prototype.action somehow?
thanks!
I've used a bespoke version of something like co to get a db.exec function which uses yield to do database request. You can pass parameters into a generator function (I pass in a connection object - see the comment where I do it).
Here is by db.exec function that is very similar to what co does
exec(generator) {
var self = this;
var it;
debug('In db.exec iterator');
return new Promise((accept,reject) => {
debug('In db.exec Promise');
var myConnection;
var onResult = lastPromiseResult => {
debug('In db.exec onResult');
var obj = it.next(lastPromiseResult);
if (!obj.done) {
debug('db.exec Iterator NOT done yet');
obj.value.then(onResult,reject);
} else {
if (myConnection) {
myConnection.release();
debug('db.exec released connection');
}
accept(obj.value);
debug('db.exec Promise Resolved with value %d',obj.value);
}
};
self._connection().then(connection => {
debug('db.exec got a connection');
myConnection = connection;
it = generator(connection); //This passes it into the generator
onResult(); //starts the generator
}).catch(error => {
logger('database', 'Exec Function Error: ' + error.message);
reject(error);
});
});
}
the connection object also wraps by database connection object and provides a generator function ability to process the rows of the results from the database, but I won't post that here (although the example below is using it to process the rows).
Here is an example of using the exec function to run a sequence of sql
db.exec(function*(connection) {
if (params.name === ADMIN_USER) {
debug('Admin Logon');
user.name = ADMIN_DISPLAY;
user.keys = 'A';
user.uid = 0;
let sql = 'SELECT passwordsalt FROM Admin WHERE AdminID = 0';
connection.request(sql);
yield connection.execSql(function*() {
let row = yield;
if (row) {
user.nopass = (row[0].value === null);
} else {
user.nopass = false;
}
debug('Admin Password bypass ' + user.nopass.toString());
});
} else {
debug('Normal User Logon');
let sql = `SELECT u.UserID,PasswordSalt,DisplayName,AccessKey,l.LogID FROM Users u
LEFT JOIN UserLog l ON u.userID = l.userID AND DATEDIFF(D,l.LogDate,GETDATE()) = 0
WHERE u.UserName = #username`;
let request = connection.request(sql);
request.addParameter('username',db.TYPES.NVarChar,params.name);
let count = yield connection.execSql(function*() {
let row = yield;
if (row) {
user.uid = row[0].value;
user.name = row[2].value;
user.keys = (row[3].value === null) ? '' : row[3].value;
user.nopass = (row[1].value === null) ;
user.lid = (row[4].value === null) ? 0 : row[4].value;
debug('Found User with uid = %d and lid = %d, keys = %s',
user.uid, user.lid, user.keys);
}
});
if (count === 0) {
debug('Not Found User');
// couldn't find name in database
reply(false,false);
return;
}
}
if (!user.nopass) {
debug('Need a Password');
//user has a password so we must check it
passGood = false; //assume false as we go into this
let request = connection.request('CheckPassword');
request.addParameter('UserID',db.TYPES.Int,user.uid);
request.addParameter('password',db.TYPES.VarChar,params.password);
yield connection.callProcedure(function*() {
let row = yield;
if (row) {
//got a valid row means we have a valid password
passGood = true;
}
});
} else {
passGood = true;
}
if (!passGood) {
debug('Not a Good Pasword');
reply(false,true);
} else {
if (user.uid !== 0 && user.lid === 0) {
let sql = `INSERT INTO UserLog(UserID,LogDate,TimeOn,UserName) OUTPUT INSERTED.logID
VALUES(#uid,GETDATE(),GETDATE(),#username)`;
let request = connection.request(sql);
request.addParameter('uid',db.TYPES.Int,user.uid);
request.addParameter('username',db.TYPES.NVarChar,user.name);
yield connection.execSql(function*() {
let row = yield;
if (row) {
user.lid = row[0].value;
debug('Users Log Entry = %d',user.lid);
}
});
}
reply(true,user);
}
})
.catch((err) => {
logger('database','Error on logon: ' + err.message);
reply(false,false);
});
});
There is a quite simple way to do async function in Commander.js
async function run() {
/* code goes here */
}
program
.command('gettime')
.action(run);
program.parse(process.argv);
I try to use limit : count with transform observer in Meteor and don't understand how to do it without "dirty" solutions.
Code I have on Client (not all, but main part)
var self = this;
self.autorun(function() {
self.subscribe('posts', Session.get('count')); // some Number like 10
}); // client
And on server where I try to use it
Meteor.publish('posts', function(count){
check(count, Number);
let i = 0;
var transform = function(doc) {
console.log(i,count);
if (i < count){ // I try something here
doc.description = new Date();
i++;
return doc;
}
else self.ready();
}
var self = this;
var observer = Posts.find().observe({
added: function (document) {
self.added('posts', document._id, transform(document));
},
changed: function (newDocument, oldDocument) {
self.changed('posts', document._id, transform(newDocument));
},
removed: function (oldDocument) {
self.removed('posts', oldDocument._id);
}
});
self.onStop(function () {
observer.stop();
});
self.ready();
});
Any idea how to limit count of shown documents with transform in publish ?
Just use Posts.find({},{limit:count}) in your query.
Here is a sample of the working async code without mongodb. The problem is, if i replace the vars (data1_nodb,...) with the db.collection.find(); function, all needed db vars received at the end and the for()-loop ends not correct. Hope someone can help. OA
var calc = new Array();
function mach1(callback){
error_buy = 0;
// some vars
for(var x_c99 = 0; x_c99 < array_temp_check0.length;x_c99++){
// some vars
calc[x_c99] = new Array();
calc[x_c99][0]= new Array();
calc[x_c99][0][0] = "dummy1";
calc[x_c99][0][1] = "dummy2";
calc[x_c99][0][2] = "dummy3";
calc[x_c99][0][3] = "dummy4";
calc[x_c99][0][4] = "dummy5";
function start_query(callback) {
data1_nodb = "data1";
data2_nodb = "data2";
data3_nodb = "data3";
data4_nodb = "data4";
calc[x_c99][0][0] = data1_nodb;
calc[x_c99][0][1] = data2_nodb;
calc[x_c99][0][2] = data3_nodb;
callback(data1_nodb,data2_nodb,etc..);
}
start_query(function() {
console.log("start_query OK!");
function start_query2(callback) {
data4_nodb = "data5";
data5_nodb = "data6";
data6_nodb = "data7";
calc[x_c99][0][3] = data4_nodb;
calc[x_c99][0][4] = data5_nodb;
callback(data5_nodb,data6_nodb,etc..);
}
start_query2(function() {
console.log("start_query2 OK!");
function start_query3(callback) {
for(...){
// do something
}
callback(vars...);
}
start_query3(function() {
console.log("start_query3 OK!");
});
});
});
}
callback(calc);
};
function mach2(callback){
mach1(function() {
console.log("mach1 OK!");
for(...){
// do something
}
});
callback(calc,error_buy);
};
mach2(function() {
console.log("mach2 OK 2!");
});
You need to work with the async nature of the collection.find() method and wait for all of them to be done. A very popular approach is to use the async module. This module allows you run several parallel tasks and wait for them to finish with its async.parallel() method:
async.parallel([
function (callback) {
db.foo.find({}, callback);
},
function (callback) {
db.bar.find({}, callback);
},
function (callback) {
db.baz.find({}, callback);
}
], function (err, results) {
// results[0] is the result of the first query, etc
});