I've got following code
var data=[];
var i = 0,
j = 9;
async.whilst(function () {
return i <= j;
}, function (next) {
connection.query('select * from table', function (err,rows, field) {
data.push(rows.length);
console.log(data);
});
i++;
next();
}, function (err) {
console.log(data);
});
I want to execute the query first and then return result. How should I do it. I've also done it with simple for loop but does not work.
I think you just need to call next() after getting the result of the query:
var data = [];
var i = 0;
var j = 9;
async.whilst(
function () { return i <= j; },
function (next) {
i++;
connection.query('select * from table', function(err, rows, field) {
data.push(rows.length);
console.log(data);
next();
});
},
function (err) {
console.log(data);
}
);
Here is another simple solution with async/await if you use babeljs:
(async function() {
let data = [];
let i = 0;
const j = 9;
while (i <= j) {
let length = await new Promise((resolve, reject) => {
connection.query('select * from table', function(err, rows, field) {
if (err) return reject(err);
resolve(rows.length);
});
});
data.push(length);
}
return data;
})()
Related
I'm using redis and nodejs for the first time, without success. Trying to loop insert data but got an empty array.
const redis = require("redis");
const client = redis.createClient({
retry_strategy: function(options) {
if (options.error && options.error.code === "ECONNREFUSED") {
// End reconnecting on a specific error and flush all commands with
// a individual error
return new Error("The server refused the connection");
}
if (options.total_retry_time > 1000 * 60 * 60) {
// End reconnecting after a specific timeout and flush all commands
// with a individual error
return new Error("Retry time exhausted");
}
if (options.attempt > 10) {
// End reconnecting with built in error
return undefined;
}
// reconnect after
return Math.min(options.attempt * 100, 3000);
},
});
var data_value = {
id: '235235',
totalrv: 'WAIT',
product: 'productName2',
url: 'url2',
process: 'proc',
task: 'msg'
};
client.set("key0", JSON.stringify(data_value));
client.set("key1", JSON.stringify(data_value));
client.set("key2", JSON.stringify(data_value));
client.set("key3", JSON.stringify(data_value));
client.set("key4", JSON.stringify(data_value));
//client.get("key2", redis.print);
var logger_data = {
logger: []
};
client.keys('*', function (err, keys) {
if (err) return console.log(err);
for(var i = 0, len = keys.length; i < len; i++) {
var values_v = client.get(keys[i].toString(), function(err, val) {
// console.log(logger_data);
// data is exist ...
logger_data.logger.push(JSON.parse(val));
});
}
});
// empty data
console.log(logger_data);
I wrote 2 print data result, in the loop it's working ok, but end of function, there are no data in array.
you can call a function inside the callback if you want to print the logger_data with values outside the asynchronous callback, like this
function printLoggerData(){
console.log(logger_data);
}
client.keys('*', function (err, keys) {
if (err) return console.log(err);
for(var i = 0, len = keys.length; i < len; i++) {
var values_v = client.get(keys[i].toString(), function(err, val) {
// console.log(logger_data);
// data is exist ...
logger_data.logger.push(JSON.parse(val));
// calling the function here so that it contains the latest values
printLoggerData();
});
}
});
Ok, with help of CertainPerformance, it's now working in asynchronous.
Thank you very much ...
async function getMessage () {
var logger_data = {
logger: []
};
return new Promise(function(resolve, reject) {
client.keys('*', function (err, keys) {
if (err) return console.log(err);
for(var i = 0, len = keys.length; i < len; i++) {
var values_v = client.get(keys[i].toString(), function(err, val) {
logger_data.logger.push(JSON.parse(val));
resolve(logger_data);
});
}
});
});
}
async function main() {
let message = await getMessage();
console.log(message);
}
main();
I am trying to finish my script, but for some reason i don't know, it refuses to execute in the order i put it in.
I've tried placing a 'wait' function between the JoinRequest update function and the following code, but when run, it acts as if the function call and wait function were the other way round, countering the point of the wait().
const Roblox = require('noblox.js')
var fs = require('fs');
var joinRequests = []
...
function wait(ms) {
var d = new Date();
var d2 = null;
do { d2 = new Date(); }
while(d2-d < ms*1000);
};
...
function updateJReqs() {
Roblox.getJoinRequests(4745601).then((array) => {
var i;
var final = [];
for(i = 0; i < array.length; i++) {
final.push(array[i].username);
};
if(final === '') {
final = '-None';
};
joinRequests = final
console.log('Updated join requests.')
});
}
function check() {
setTimeout(() => {
fs.readFile('Request.txt',encoding = 'utf-8', function(err, data) {
if (err) {
check();
} else {
updateJReqs(); //for some reason this function is executed alongside the below, not before it.
// Tried putting wait(x) in here.
console.log('Request received: ' + data)
var solution = joinRequests
console.log('Fuffiling request with ' + solution)
fufillRequest(solution)
fs.unlink('Request.txt', function(err) {
if(err) throw err;
});
check();
}
});
}, 400)
}
check();
The script is supposed to wait until a file is created (accomplished), update the list of join requests (accomplished) and then create a new file with the list of join requests in(not accomplished).
if I understand your code you work with async code, you need to return a promise in updateJReqs and add a condition of leaving from the function because you have an infinite recursion
function updateJReqs() {
return new Promise(resolve => {
Roblox.getJoinRequests(4745601).then((array) => {
var i;
var final = [];
for(i = 0; i < array.length; i++) {
final.push(array[i].username);
};
if(final === '') {
final = '-None';
};
joinRequests = final
console.log('Updated join requests.')
resolve();
});
}
}
async function check() {
setTimeout(() => {
fs.readFile('Request.txt',encoding = 'utf-8', function(err, data) {
if (err) {
await check();
} else {
await updateJReqs();
// Tried putting wait(x) in here.
console.log('Request received: ' + data)
var solution = joinRequests
console.log('Fuffiling request with ' + solution)
fufillRequest(solution)
fs.unlink('Request.txt', function(err) {
if(err) throw err;
});
// you dont have an exit from your function check();
return 'Success';
}
});
}, 400)
}
check().then(res => console.log(res));
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
});
});
}
So i have this 2-layer query in node.js, each query could return multiple results. My code actually just ignores that for now. This is the best i can get, it seems working.
How to correct it please, i don't know how to callback for the 2nd one.
Also the db.close() is always called before the 2nd query finishes, even i have serialize().
var getInfo1Db = function(callback) {
var db = new sqlite3.Database("DB.sqlite3");
var cnt = 0;
var info1JsonObj = [];
db.all("select * from Info1DB",
function(err, rows) {
db.serialize(function() {
for(var ii=0, len=rows.length; ii<len; ii++) {
var t2 = rows[ii].info1;
var doorId = ...
db.all("select * from DoorDB where ObjectID=" + doorId,
function(err, row2) {
if(err) {
} else {
var doorName = row2[0]...
var info1JsonElem = {
"DoorName" : doorName
};
info1JsonObj.push(info1JsonElem);
cnt++;
if(cnt === rows.length) {
callback(null, info1JsonObj);
}
}
}
); // for the only door info based on door id
} // for each row of info1
db.close(); // why this finishes before the 2nd db.all
} ); // end of serialize
});
};
You can't implement nested query in sqlite3's normal way. ( I mean you even can't do it in the callback hell way, because the sqlite3 need to close the connection before another query called. otherwise you will always got error)
You have to use Promise, async and await to do this.
( it's worth to spend 30 minutes to learn these 3 words )
Step1. define a async function like this:
async query_1() {
new Promise(resolve => {
db = ...
db.serialize( () => {
db.get('select .. from ... where id = 1', [], (error, row) => {
// here is the KEY: put the result into resolve
// this equals to the "return" statement in non-sync method.
resolve(row)
}
})
db.close()
})
}
and also implement your query_2 function like this:
async query_2() {
let query_1_result = await this.query_1()
db = ...
db.serialize( () => {
db.get('select .. from ... where dependency_id = ' + query_1_result, [], (error, row) => {
// other code here...
}
})
db.close()
}
refer to my answer: https://stackoverflow.com/a/67881159/445908
How about using 2 function to do these ?
function db_query1(your_param,...., callback){
// database operation
db.run( sql , [param,...] , function(err,rows){
if(err) // return
else{
// get rows with callback
callback(null, rows);
}
});
}
function db_query2(your_param,...., callback){
// database operation
db.run( sql , [param,...] , function(err,rows){
if(err) // return
else{
// get rows with callback
callback(null, rows);
}
});
}
And call these function:
db_query1(....,function(err,result1){
if(err) ...// return
// do the things with result1
// And then call query2
db_query2(....,function(err,result2){
if(err) ...// return
// do the things with result1
});
});
Hope this will help :)
You can use Promises.all, an array and the second callback for node sqlite3 db.each() that is executed when all rows have been fetched. Node Sqlite3 db.each usage to simplify the nested query and
I cannot really get the meaning of the variables you are using thus I assume that each row in Info1DB has a one-to-many relationship with DoorDB on the field doorId.
async function getInfo (callback) {
sql = "select * from Info1DB;";
numVersions = 0;
countVersions = 0;
info1JsonObj = [];
db.serialize(function() {
db.each(sql, [], (err, info1Row) => {
sql = "select * from DoorDB where ObjectID=?;";
info1Row.doors = [];
doorId = ...
db.each(sql, [doorId], (err, doorRow) => {
info1Row.doors.push(new Promise((resolve, reject) => {
if (err) {
reject(err);
} else {
resolve(doorRow);
}
}));
}, (err, num) => {
Promise.all(info1Row.doors)
.then((doors) => {
info1Row.doors = doors;
info1JsonObj.push(info1Row);
countVersions++;
if (countVersions == numVersions) {
callback(null, info1JsonObj);
}
}).catch((err) => {
callback(err, null);
});
});
}, (err, versions) => {
numVersions = versions;
});
});
}
I want to insert multiple data by for loop , but this code add 2 or 3 data only , then its continue loading loading but nothing happen ...
router.post('/addclient' , function (req , res){
var finished = false;
var user = req.body.username;
for(var i = 0 ; i <30 ; i++){
req.body.username = user + i ;
objDB.insert("clientList" ,req.body, function(err, data){
//if(err) console.log(err);
if(i>20){
finished = true;
}
});
}
if(finished){
res.redirect('/client/client-list');
}
});
you are doing it wrong. insert is asynchronous, so when insert for i=1 completes and callback gets called, maybe i is equal to 20 and more and you can't guess it. you are missing synchronous and asynchronous concepts and differences.
here is two solutions for your problem :
first, adding 30 items at once :
var clientsList = [];
for (var i = 0 ; i < 30 ; i++) {
clientsList[i] = Ith client object; // create object you want to insert for client i
}
// for example insertAtOnce is a function to insert your list
objDB.insertAtOnce(clientsList,function(err,callback) {
if (err) console.log("error : ", err);
res.redirect('/client/client-list');
});
second, using bind
function insertCallback(itr, res, err,callback) {
if (itr == 29) {
res.redirect('/client/client-list');
}
}
----
for(var i = 0 ; i <30 ; i++){
req.body.username = user + i ;
objDB.insert("clientList" ,req.body,insertCallback.bind(null, i, res);
}
Would be best if you use the async node.js library which provides control flows like running each function in series. You could use the async.whilst() method and restructure your code as:
router.post('/addclient', function(req, res) {
var user = req.body.username,
count = 0,
result = { finished = false };
async.whilst(
function () { return count < 30; },
function (callback) {
count++;
req.body.username = user + count.toString();
objDB.insert("clientList", req.body, function(err, data){
if (err) { return callback(err); }
result["data"] = data;
if( count > 20 ) result.finished = true;
callback(null, result);
});
},
function (err, result) {
if (err) { /* handle err */};
if (result.finished) res.redirect('/client/client-list');
}
);
});
You have a callback called after running insert function. It runs not exactly after running insert, and not in loop(it asynchronous). So in your code res.redirrect will never be called, because finished will be true after all loop will run. If you don't need to have all this inserts finished before answer, you can go this way:
if(i == 29){
res.redirect('/client/client-list');
}
Otherwise you need to create some queue, for example, i'm using async library https://github.com/caolan/async to create queues and running callbacks after queue ends.
router.post('/addclient', function(req, res) {
var finished = false;
var user = req.body.username;
var i = 0;
while( true ) {
if ( i > 20 ) {
res.redirect('/client/client-list');
}
req.body.username = user + i;
var promise = new Promise();
objDB.insert("clientList", req.body, function(err, data) {
promise.resolve();
});
promise.then(function() {
i++;
continue;
});
}
});
I have written it from the top of my head. But the basic idea here is that you need a loop to run infinitely, then resolve a promise; the resolution triggers continuing the loop, and increment the counter.
Use Promise. I would have done something like below
router.post('/addclient' , function (req , res){
var finished = false;
var promise = [];
var user = req.body.username;
for(var i = 0 ; i <30 ; i++) {
req.body.username = user + i;
promise.push(new Promise(resolve, reject) {
objDB.insert("clientList" ,req.body, function(err, data) {
if(err) {
reject(err)
return
}
resolve(data)
})
})
}
Promise.all(promise).then(function() {
finished = true
})
if(finished){
res.redirect('/client/client-list');
}
});