I have PHP website in which, chat module is working fine ( via ajax ).
Now I am creating Ionic app for this chat module, So I am trying to convert my PHP code on NODE.js
To get a list of chat users i wrote this code in helper.js file
setMessage:function(message1){
message=message1;
},
setPeople:function(id,people1){
people[id]=people1;
},
setChatlist:function(data9){
chatlist.push(data9);
},
setRecorder:function(data8){
recorder.push(data8);
},
getUserChatList:function(uid,connection,callback){
chatlist=[];
recorder=[];
people=[];
message={};
var data={
query:"select id from messages where recipient_id='"+uid+"' or timeline_id='"+uid+"' order by timestamp desc ",
connection:connection
}
var db_conncetion=data.connection;
var query=data.query;
var insert_data=data.insert_data;
db_conncetion.getConnection(function(err,con){
if(err){
con.release();
}else{
con.query(String(query),insert_data,function(err,rows){
if(!err) {
if(rows.length>0){
query1="select DISTINCT recipient_id from messages where timeline_id='"+uid+"' order by timestamp desc ";
con.query(String(query1),insert_data,function(err1,rows1){
rows1.forEach(function(element1, index1, array1){
var receiverId=element1.recipient_id;
var receiverSql = "SELECT time,text FROM messages WHERE timeline_id=" +uid+ " AND recipient_id=" +receiverId+" ORDER BY time DESC";
con.query(String(receiverSql),insert_data,function(err2,rows2){
rows2.forEach(function(element2, index2, array2){
people[receiverId]=element2.time;
message[receiverId]=element2.text;
});
self.setMessage(message);
self.setPeople(people,people);
});
});
});
var senderIdSql = "SELECT DISTINCT timeline_id FROM messages WHERE recipient_id=" +uid+ " ORDER BY time DESC";
con.query(String(senderIdSql),insert_data,function(err3,rows3){
rows3.forEach(function(element1, index1, array1){
var senderId=element1.timeline_id;
var senderSql = "SELECT time,text FROM messages WHERE recipient_id=" +uid+ " AND timeline_id=" +senderId+ " ORDER BY time DESC";
con.query(String(senderSql),insert_data,function(err2,rows2){
rows2.forEach(function(element2, index2, array2){
if (!self.isset(people[senderId]) || element2.time > people[senderId])
people[senderId]=element2.time;
message[senderId]=element2.text;
self.setPeople(senderId,element2.time);
self.setMessage(message);
});
});
});
});
}
Object.keys(people).forEach(function (key){
var tempArray={};
tempArray['id']=key;
tempArray['text']=message[key];
self.setRecorder(tempArray);
});
recorder.forEach(function (key){
var user_query="SELECT * FROM accounts WHERE id=" +key +" AND active=1 ";
con.query(String(user_query),insert_data,function(err3,rows3){
var tmp1=[];
rows3.forEach(function(element2, index2, array2){
var data1={};
data1['receiver_id']=element2.id;
data1['receiver_username']=element2.username;
data1['receiver_name']=element2.name;
data1['receiver_thumbnail_url']=element2.thumbnail_url;
data1['receiver_online']=0;
data1['receiver_message'] = recorder[key];
tmp1.push(data1);
});
self.setChatlist(tmp1);
});
});
var ret_data={};
ret_data['status']=200;
ret_data['success']=1;
ret_data['messages']=chatlist;
console.log(ret_data);
console.log("1111");
callback(ret_data);
con.release();
//console.log(message);
} else {
console.log(err);
console.log("Query failed");
}
});
}
});
}
But when i am calling this method via socket it's giving an empty array
listening in http://localhost:3000
{ status: 200, success: 1, messages: [] }
1111
Please tell why it's giving an empty array?
It is supposed to be an empty array according to your current code.
All the db calls will be asynchronous and will not wait for its completion. It will execute the next line which will execute the following code before the db calls get finished:
var ret_data = {};
ret_data['status'] = 200;
ret_data['success'] = 1;
ret_data['messages'] = chatlist;
console.log(ret_data);
console.log("1111");
callback(ret_data);
con.release();
//console.log(message);
So your callback gets executed with initial value that is [] and thus you have the value as [].
You have to manage the db calls and the data to be sent. You can use promises or async/await to this. The code will be much more clean and traceable. Take a good look at them.
Related
I am using MongoDB and Node.JS, I am trying to get data out of my MongoDB and show into my html page which I have working with the below code however this just brings back ALL entries in no particular order:
server.js
// This is for getting the list of all players from my DB
app.get("/getPlayers", function(request, response) {
db.getPlayers().then(function(players){
console.log(players);
response.send(players);
});
});
leadership.html
<script>
$(function() {
$.get("http://localhost:9000/getPlayers", {}, function (res) {
let data = res;
console.log(res);
for (i = 0; i < data.length; i++) {
let name = data[i].name;
let score = data[i].score;
console.log(data[i].name);
$("#leadership").append("<tr><td class=\"name\">"
+ data[i].name + "</td><td class=\"score\">"
+ data[i].score + "</td></tr>");
}
});
});
</script>
After looking at W3 Schools I tried to alter the code to this:
db.getPlayers().sort().limit(10).then(function(players)
However my Chrome console brings back an internal server error 500. Can someone point out how I can sort by LARGEST NUMBER first, then LIMIT the results to say 10? Within the database there is a collection called players, which holds name and score
db.js
var Player = mongoose.model("Player", {name: String, score: Number});
module.exports.Player = Player;
Try something like this.
Order, sort and limit can be passed from front end or change default values after : mark.
Players is imported model, you can do it this way or use method in the model itself.
app.post('/api/players',(req,res)=>{
let order = req.body.order ? req.body.order : "-1";
let sortBy = req.body.sortBy ? req.body.sortBy : "_id";
let limit = req.body.limit ? parseInt(req.body.limit) : 100;
Players.
find().
sort([[sortBy,order]]).
limit(limit).
exec((err,players)=>{
if(err) return res.status(400).send(err);
res.status(200).json({
size: players.length,
players
})
})
})
I'm training do display the current value from my firebase database
on to my HTML counter.
the problem is that I see only the current clicks and not the total clicks
in the console, I can see the database value + 1
var bunnyData = null;
function thumbsUpBtn(val) {
var count = document.getElementById('like').value;
var new_count = parseInt(count ,10) + val;
if (new_count < 0) {
new_count = 0;
}
var videosList = firebase.database().ref().child('videos');
videosList.on("value", function(snapshot) {
var allVideos = snapshot.val();
bunnyData = allVideos.bunny;
console.log( bunnyData.likeCount);
WriteStatsToPage();
});
onclick
videosList.child("bunny").set({
likeCount : bunnyData.likeCount+1,
dislikeCount : bunnyData.dislikeCount,
viewsCount : 100
});
function WriteStatsToPage(){
$("likeNUmber").html[bunnyData.likeCount];
}
document.getElementById('like').value = new_count ;
return new_count ;
}
<button id="thumbsUp" onClick="thumbsUpBtn(1)">
<img class="likeImg" src="Like.png" >
<input id="like" value="0" ></button>
Transactions and Batched Writes
Transactions are useful when you want to update a field's value based
on its current value, or the value of some other field. You could
increment a counter by creating a transaction that reads the current
value of the counter, increments it, and writes the new value to Cloud
Firestore.
A transaction consists of any number of get() operations followed by
any number of write operations such as set(), update(), or delete().
In the case of a concurrent edit, Cloud Firestore runs the entire
transaction again. For example, if a transaction reads documents and
another client modifies any of those documents, Cloud Firestore
retries the transaction. This feature ensures that the transaction
runs on up-to-date and consistent data.
// Create a reference to the SF doc.
var sfDocRef = db.collection("cities").doc("SF");
// Uncomment to initialize the doc.
// sfDocRef.set({ population: 0 });
return db.runTransaction(function(transaction) {
// This code may get re-run multiple times if there are conflicts.
return transaction.get(sfDocRef).then(function(sfDoc) {
var newPopulation = sfDoc.data().population + 1;
transaction.update(sfDocRef, { population: newPopulation });
});
}).then(function() {
console.log("Transaction successfully committed!");
}).catch(function(error) {
console.log("Transaction failed: ", error);
});
I wrote a ~50 lines script to perform housekeeping on MySQL databases. I'm afraid my code exhibits anti-patterns as it rapidly escalates to an unreadable mess for the simple functions it performs.
I'd like some opinions for improving readability.
The full script is at the bottom of this post to give an idea.
Spotlight on the problem
The excessive nesting is caused by patterns like this repeated over and over: (snippet taken from script)
sql.query("show databases")
.then(function(rows) {
for (var r of rows) {
var db = r.Database;
(function(db) {
sql.query("show tables in " + db)
.then(function(rows) {
// [...]
}
})(db);
}
});
I'm nesting one promise under the other within both a for loop and a closure. The loop is needed to iterate across all results from sql.query(), and the closure is necessary to pass the value of db to the lower promise; without the closure, the loop would complete even before the nested promise executes at all, so db would always contain only the last element of the loop, preventing the nested promise from reading each value of db.
Full script
var mysql = require("promise-mysql");
var validator = require("mysql-validator"); // simple library to validate against mysql data types
var ignoreDbs = [ "information_schema" ],
multiplier = 2, // numeric records multiplier to check out-of-range proximity
exitStatus = {'ok': 0, 'nearOutOfRange': 1, 'systemError': 2};
(function() {
var sql,
mysqlHost = "localhost",
mysqlUser = "user",
mysqlPass = "";
mysql.createConnection({
host: mysqlHost,
user: mysqlUser,
password: mysqlPass
}).then(function(connection) {
sql = connection;
})
.then(function() {
sql.query("show databases")
.then(function(rows) {
for (var r of rows) {
var db = r.Database;
if (ignoreDbs.indexOf(db) != -1) continue;
(function(db) {
sql.query("show tables in " + db)
.then(function(rows) {
for (var r of rows) {
var table = r["Tables_in_" + db];
(function(table) {
sql.query("describe " + db + "." + table)
.then(function(rows) {
for (var r of rows) {
(function(r) {
var field = r.Field,
type = r.Type, // eg: decimal(10,2)
query = "select " + field + " from " + db + "." + table + " ";
if (table != "nonce") query += "order by date desc limit 1000";
sql.query(query)
.then(function(rows) {
for (var r of rows) {
var record, err;
// remove decimal part, only integer range is checked
record = Math.trunc(r[field]);
err = validator.check(record * multiplier, type);
if (err) {
console.log(err.message);
process.exit(exitStatus.nearOutOfRange);
}
}
});
})(r);
}
});
})(table);
}
});
})(db);
}
});
})
.then(function() {
// if (sql != null) sql.end(); // may not exit process here: sql connection terminates before async functions above
//process.exit(exitStatus.ok); //
});
})();
Trivia
The purpose of the script is to automatically and periodically monitor if any record stored in any row, table and database in MySQL is approaching the out-of-range limit for its specific data type. Several other processes connected to MySQL continuously insert new numeric data with increasing values and nonces; this script is a central point where to check for such numeric limits. The script would then be attached to Munin for continuous monitoring and alerting.
Update: Revised script
As suggested by #Kqcef I modularized the anonymous functions out of the promise nest, and used let to avoid the explicit nesting of an additional function to preserve variable context.
Still this is excessively verbose, previously I wrote the same script in Bash in about 40 lines, but performance was screaming for a port to nodejs.
"use strict";
var mysql = require("promise-mysql");
var validator = require("mysql-validator"); // a simple library to validate against mysql data types
var ignoreDbs = [ "information_schema" ],
multiplier = 2, // numeric records multiplier to check out-of-range proximity
exitStatus = {'ok': 0, 'nearOutOfRange': 1, 'systemError': 2};
var mysqlHost = "localhost",
mysqlUser = "btc",
mysqlPass = "";
// return array of DBs strings
function getDatabases(sql) {
return sql.query("show databases")
.then(function(rows) {
var dbs = [];
for (var r of rows)
dbs.push(r.Database);
return dbs;
});
}
// return array of tables strings
function getTables(sql, db) {
return sql.query("show tables in " + db)
.then(function(rows) {
var tables = [];
for (var r of rows)
tables.push(r["Tables_in_" + db]);
return tables;
});
}
// return array of descriptions
function getTableDescription(sql, db, table) {
return sql.query("describe " + db + "." + table)
.then(function(rows) {
var descrs = [];
for (var r of rows) {
descrs.push({ 'field': r.Field, // eg: price
'type': r.Type}); // eg: decimal(10,2)
}
return descrs;
});
}
// return err object
function validateRecord(record, type) {
var record, err;
if (typeof record != "number") {
console.log("error: record is not numeric.");
process.exit(exitStatus.systemError);
}
// remove decimal part, only integer range is checked
record = Math.trunc(record);
err = validator.check(record * multiplier, type);
return err;
}
(function() {
var sql;
mysql.createConnection({
host: mysqlHost,
user: mysqlUser,
password: mysqlPass
}).then(function(connection) {
sql = connection;
})
.then(function() {
return getDatabases(sql)
})
.then(function(dbs) {
dbs.forEach(function(db) {
if (ignoreDbs.indexOf(db) != -1) return;
getTables(sql, db)
.then(function(tables) {
tables.forEach(function(table) {
getTableDescription(sql, db, table)
.then(function(descrs) {
descrs.forEach(function(descr) {
let field = descr.field,
type = descr.type,
query = "select " + descr.field + " from " + db + "." + table + " ";
if (table != "nonce") query += "order by date desc limit 1000";
sql.query(query)
.then(function(rows) {
rows.forEach(function(row) {
let err = validateRecord(row[field], type);
if (err) {
console.log(err.message);
process.exit(exitStatus.nearOutOfRange);
}
});
});
});
});
});
});
});
});
/*
.then(function() {
//if (sql != null) sql.end();
//process.exit(exitStatus.ok);
});
*/
})();
I agree with Jaromanda in terms of using let in your for loops to block scope the values and avoid your usage of an immediately-invoked function, which, while totally fine in terms of functionality, is decidedly less readable.
In terms of best practices and avoiding anti-patterns, one of the most important things you can strive for in terms of writing 'good' code is building modularized, reusable blocks of code. As it stands, your code has 5 or 6 anonymous functions that exist nowhere but within your chain of promise callbacks. If you were to declare those as functions outside of that chain, not only does that improve the maintainability of your code (you can test each individual one), but, if their names are clearly indicative of their purposes, would make for a very readable promise chain.
(Updated based on User Question)
Rather than leaving inner functions...
function getTableDescription(sql, db, table) {
return sql.query("describe " + db + "." + table)
.then(function(rows) {
var descrs = [];
for (var r of rows) {
descrs.push({ 'field': r.Field, // eg: price
'type': r.Type}); // eg: decimal(10,2)
}
return descrs;
});
}
...you can easily strip that out so that your code is self-documenting:
function collectDescriptionsFromRows(rows) {
var descriptions = [];
for (var row of rows) {
descriptions.push({'field': row.Field, 'type': row.Type});
}
return descriptions;
}
function getTableDescription(sql, db, table) {
return sql.query("describe " + db + "." + table)
.then(collectDescriptionsFromRows);
}
Also, if you ever find yourself doing data collection from one array to another, it's extremely helpful to get used to using built-in higher order functions (map, filter, reduce). Instead of the collectDescriptionsFromRows I just listed, it could be simplified to:
function collectDescriptionsFromRows(rows) {
return rows.map(row => { 'field': row.Field, 'type': row.Type});
}
Much less verbose, much more readable. Your code and promise-chain will shrink and read more like a step-by-step list of instructions if you continue to extract those anonymous functions in the chain. Anywhere you see function(...there is more extracting to do! You can also do some damage (positively) by extracting all the data you need to begin with and use local logic to boil it down to what you need, rather than making several queries. Hope this helps.
This question already has answers here:
Wait until all jQuery Ajax requests are done?
(22 answers)
Closed 7 years ago.
I m working on phonegap product using jquery and jquery mobile, the scenario is, when user is logging in for first time, we sync all the data and after done we forward user to another view. The items are retrieved in json format from server. Here are the portion of my code. I have called the webservice and the response is returned as JSON objects in response variable.
$(response.data.module.registration).each(function(k,v){
//insert into app's sqlite database
});
$(response.data.module.attendance).each(function(k,v){
//insert into app's sqlite database
});
$(response.data.items.grocery).each(function(k,v){
//insert into app's sqlite database
});
//and so on. There could be many rows in each loop above.
My question is how to know all rows has been inserted from the loop so that I can forward user to restricted area.
more precisely, how to know all JSON object has been iterated successfully?
What i tried is put counter in each loop and check if sum of all the counters is equal to total items we are iterating. But this didn't work the sum of all the counters are readily available before all items are inserted.
EDIT
Here is my helper function that inserts record into sqlite db. This didn't work, user was logged in before all data are inserted. Can you tell me where I went wrong
var sqlhelper = {
insertJSONData:function(tablename,data,callback){
var dfrd = $.Deferred();
var fields=sqlhelper.separateFieldData(data,"field");
var dataval=sqlhelper.separateFieldData(data,"value");
sqlhelper.db.transaction(function(tx) {
var sqlquery='INSERT INTO '+tablename+' ('+fields+') values('+dataval+')';
console.log(sqlquery);
tx.executeSql(sqlquery,[],function(tx,result){
dfrd.resolve(result);
console.log('Success');
},sqlhelper.errorCB);
if(callback!=undefined){
callback();
}
});
return dfrd.promise();
}
}
And here is the code that fetches server response
function defObj1()
{
if(typeof response.data.module.registration!="undefined"){
$(response.data.module.registration).each(function(i,e){
var data = {
'reg_id': e.reg_id,
'reg_name': e.reg_name,
'reg_desc': e.reg_desc,
'reg_status': e.reg_status
};
sqlhelper.insertJSONData('tbl_registration',data);
}); // end of each loop
}
}
function defObj2()
{
if(typeof response.data.items.grocery!="undefined"){
$(response.data.items.grocery).each(function(i,e){
var data = {
'grocery_id': e.grocery_id,
'item_name': e.item_name,
'item_qty': e.item_qty,
'item_unit_price': e.item_unit_price
};
sqlhelper.insertJSONData('tbl_grocery',data);
}); // end of each loop
}
}
$.when(defObj1() ,defObj2()).done(function(a1,a2){
//sync complete so login user
doLogin();
})
Thanks
try this. (Edited)
var isValid = true, i = 0, sum, callback = function () {
//if all inserting is successfully it is called
};
...
$(response.data.module.registration).each(function (k, v) {
//insert into app's sqlite database
var data = {
'reg_id': e.reg_id,
'reg_name': e.reg_name,
'reg_desc': e.reg_desc,
'reg_status': e.reg_status
};
sqlhelper.insertJSONData('tbl_registration', data, function (data) {
if (!data) {
isValid = false;
sum++;
}
i++;//onSuccess function
checkLast(i);//call this lastly method or each
}, function () {
i++;//onError function
});
});
...
//other codes is identical logic
...
function checkLast(i) {
if (i == sum) {
callback();
}
}
...
I have added successCallbak and errorCallback to your sqlhelper
var sqlhelper = {
insertJSONData: function (tablename, data, successCallbak, errorCallback) {
var dfrd = $.Deferred();
var fields = sqlhelper.separateFieldData(data, "field");
var dataval = sqlhelper.separateFieldData(data, "value");
sqlhelper.db.transaction(function (tx) {
var sqlquery = 'INSERT INTO ' + tablename + ' (' + fields + ') values(' + dataval + ')';
console.log(sqlquery);
tx.executeSql(sqlquery, [], function (tx, result) {
dfrd.resolve(result);
if (successCallback) {
successCallback(result);
}
console.log('Success');
}, sqlhelper.errorCB);
if (errorCallback) {
errorCallback();
}
});
return dfrd.promise();
}
}
I am new to Mongo and Node. I am currently using Mongoskin and Bluebird to handle the db connection and queries (as suggested here: https://stackoverflow.com/a/23687958/2701348 ).
I have three collections: Users, Binders and Cards.
The Binders collection contains the information about Cards for each User.
Each document in Binders has as properties:
User Id <--- that refers to the User owning the Card
Card Code <--- that refers to a Card
Count <--- that refers to the number of cards owned by the User
I prefer to have a separate Cards collection so that when a Card changes, it changes for all the Users Binders.
Now I am willing to retrieve an array for a given user such as:
[{card: {card document}, count: 4}, ...]
I have the following problems:
the db connection should be closed after all the async db callbacks are called
the cards array should be returned after the last db.collection('cards').find gives back the results
I know my following code is wrong but can be a starting point for a discussion:
var getAllBinderCards = function(req, res){
var db = req.db;
var userId = req.userId;
var promiseBinders = db.collection('binders').find({userId: userId}).toArrayAsync();
promiseBinders.then(function(binderCards) {
if (binderCards) {
var promiseCards;
//console.log("------ binderCards: ", binderCards);
var cards = [];
for (var i = 0; i < binderCards.length; i++) {
var binderCard = binderCards[i];
promiseCards = db.collection('cards').find({Code: binderCard.Code}).toArrayAsync();
promiseCards.then(function(cardsDB){
if(cardsDB){
//console.log("Cards found: ",binderCard.Code, cardsDB);
for (var i = 0; i < cardsDB.length; i++) {
cardsDB[i].count = binderCard.count;
};
cards.concat(cardsDB);
}
});
}
promiseCards.then(function(){
db.close();
console.log("Binder Cards: " , cards);
res.json(cards);
});
}
});
}
I am struggling trying to figure out how to handle the promisfied asynchronous call correctly in order to send back the whole array and close the db connection.
I think I should try to build a promise before the for loop and use it to chain the query on Cards promises and lastly chain the db.close() and res.json(cards) statements.
[EDIT] Maybe the easiest solution is to simply use the $in filter inside a single db.collection('cards').find({Code: {$in: [bindersCodeArray] }}).toArrayAsync(); and avoid that for loop:
var getAllBinderCards = function(req, res){
var db = req.db;
var userId = req.userId;
var promiseBinders = db.collection('binders').find({userId: userId}).toArrayAsync();
promiseBinders.then(function(binderCards) {
if (binderCards) {
var binderCodes = binderCards.map(function(element){
return element.Code;
});
var promiseCards = db.collection('cards').find({Code: {$in: binderCodes} }).toArrayAsync();
promiseCards.then(function(cards){
var bindersDictionary = {};
for (var i = 0; i < binderCards.length; i++) {
bindersDictionary[binderCards[i].Code] = binderCards[i].count;
};
for (var i = 0; i < cards.length; i++) {
cards[i].count = bindersDictionary[cards[i].Code];
};
db.close();
console.log("Binder Cards: " , cards);
res.json(cards);
});
}
});
}
Still I am curious if there is an elegant way to solve this riddle using promises.
I would expect that using $in and array may have constraints on the number of binders you can pass and affect query performance. You can also try doing this with async#map. e.g.:
...
function(binders) {
async.map(binders, cardsForBinders, function(err, bindersWithCards) {
// TODO: close connection here.
}
function cardsForBinders(binder, callback) {
// 1. find cards for binder.
// 2. prepare transformed response: binderWithCards.
callback(null, binderWithCards);
}
}
...