I'm new to Nativescript and Couchbase, but when executing a query against my Couchbase database I simply want to log the results. Here is my example code:
let rows = this.database.executeQuery('profiles');
for(let i = 0; i < rows.length; i++) {
this.profiles.push(rows[i]);
}
When trying to log "rows" using console.log I get the expected [Object object]. I thought I could use console.dir, but when doing that I get:
JS: === dump(): dumping members ===
JS: "rows: "
JS: === dump(): dumping function and properties names ===
JS: 0: r
JS: 1: o
JS: 2: w
JS: 3: s
JS: 4: :
JS: 5:
JS: 6:
JS: === dump(): finished ===
Is there a way to log the actual results from executeQuery?
If you are happy to log out the results from the rows array after they have been collected, you could just use JSON.stringify(), and enumerate over the array. Which might look something like this:
rows.forEach(row => {
console.log(JSON.stringify(row))
})
Related
I need to catch some data by a mysql query, and use the result to build up and email message with its results with node.
I put the code inside a function, but the call to the query appear to still be async, as the result is never given back before the end of the function, and the returning variable is alwasy empty.
Tried different approach with async/await but still the execution seems async
In my following code is just get in the console log up to the step 3, the step 4 is mde no matter what I try to do at the end of the function call
async function querydb (utente){
console.log("sono in querydb");
var messageHTMLAllegati="";
var risultatoquery;
console.log("step 1");
var connection = mysql.createConnection({
host : process.env.IP_address,
user : process.env.nome_utente,
password : process.env.password,
port : process.env.port,
database : process.env.DB,
});
console.log("step 2");
const query = util.promisify(connection.query).bind(connection);
(async () => {
try {
console.log("step 3");
var result = await query('SELECT Link FROM Link_Foto where ID_Utente="' + utente + '"');
var i = result.length;
console.log("step 4");
var j ;
for (j=0; j < i; j++) {
messageHTMLAllegati +='Immagine ' + (j+1)+ '<BR>';
console.log("print the link found in the DB and added to the text to be printed"+result[j].Link);
}
} finally {
connection.end();
}
})()
return messageHTMLAllegati;
}
I do expect the final variable "messageHTMLAllegati" to contain some text plus the query fields needed, but it get always empty. In the log I see though that the variable is filled up, but only after that the function is returned, therefore the text used to put the email together is empty from the DB section
async/await method only works when await functions is a promise. functions like 'query' in mysql are using a callback function to get the result. So if you want to use it with async/await method you should use it in another function and get the result in its callback function as a promise like this:
function query_promise(q_string){
return new Promise((resolve, reject)=>{
query(q_string,(err, result)=>{
if(err) return reject(err);
resolve(result);
});
});
}
then in your code:
var result = await query_promise('SELECT Link FROM Link_Foto where ID_Utente="' + utente + '"');
I am missing something fundamental in terms of callbacks/async in the code below: why do I get:
[,,'[ {JSON1} ]']
[,,'[ {JSON2} ]']
(=2 console returns) instead of only one console return with one proper table, which is want I want and would look like:
[,'[ {JSON1} ]','[ {JSON2} ]']
or ideally:
[{JSON1},{JSON2}]
See my code below, getPTdata is a function I created to retrieve some JSON via a REST API (https request). I cannot get everything at once since the API I'm talking to has a limit, hence the limit and offset parameters of my calls.
offsets = [0,1]
res = []
function goGetData(callback) {
for(var a = 0; a < offsets.length; a++){
getPTdata('stories',
'?limit=1&offset='+offsets[a]+'&date_format=millis',
function(result){
//called once getPTdata is done
res[a] = result
callback(res)
});
}
}
goGetData(function(notgoingtowork){
//called once goGetData is done
console.log(res)
})
Solved like this:
offsets = [0,1]
res = []
function goGetData(callback) {
var nb_returns = 0
for(var a = 0; a < offsets.length; a++){
getPTdata('stories','?limit=1&offset='+offsets[a]+'&date_format=millis', function(result){
//note because of "loop closure" I cannot use a here anymore
//called once getPTdata is done, therefore we know result and can store it
nb_returns++
res.push(JSON.parse(result))
if (nb_returns == offsets.length) {
callback(res)
}
});
}
}
goGetData(function(consolidated){
//called once goGetData is done
console.log(consolidated)
})
I am using MEAN stack and I am sending query parameters dynamically to my Nodejs server endpoints.
My client controller :
$http.get('/api/things',{params:{query:query}}).then(response => {
this.awesomeThings = response.data;
socket.syncUpdates('thing', this.awesomeThings);
});
where query is a value injected into the controller.
This is the server controller function (which works):
export function index(req, res) {
var query = req.query.query && JSON.parse(req.query.query)
Thing.find(query).sort({_id:-1}).limit(20).execAsync()
.then(respondWithResult(res))
.catch(handleError(res));
}
The above works but I am trying to understand the line
var query = req.query.query && JSON.parse(req.query.query)
as I have never seen this before( and I don't come from a programming background). I console.logged query and understand it's an object (which is required by Mongodb) but when I console.logged (JSON.parse(req.query.query)) or JSON.parse(query) to find out the final output, the program stops working with no error messages, very strange..
If someone can explain the above syntax and why it has to be done this way for it work, that would be much appreciated..
PS when I try to console log the JSON.parse like so, it fails to load even though it should have no effect whatsoever:
export function index(req, res) {
var query = req.query.query && JSON.parse(req.query.query)
var que = JSON.parse(req.query.query)
Thing.find(query).sort({_id:-1}).limit(20).execAsync()
.then(respondWithResult(res))
.catch(handleError(res));
console.log("que"+que)
}
function one() {
var x = {};
var res = JSON.parse(x.y);
console.log(res);
}
function two() {
var x = {};
var res = x.y && JSON.parse(x.y);
console.log(res);
}
<button onclick="one()">ERROR</button>
<button onclick="two()">NO ERROR</button>
var x = data && JSON.parse(data);
Since expression is evaluated from left, first data is evaulated.
If it is undefined then, the next part -> JSON.parse() is not performed.
On the other hand, if data is defined parse is tried and the result is returned and stored in x.
Main advantage here is the parse doesn't run if the variable wasn't defined.
it could be equivalent to saying:
if(data) {x = JSON.parse(x);}
New to node, As I am cycling through a roster of students, I need to check and see if a teacher has requested them for tutoring.
I realized I can't just do this:
var checkRequest = function(id){
var value = '';
roster.query('SELECT * FROM teacher_request WHERE student_id ='+id, function(err, row){
value = row.length;
}
return value;
}
After a bit of digging around promises looked like a great solution, but if I simply return the deferred.promise from the checkRequest function, all I get is an object that says [deferred promise] which I can't access the actual data from. (Or have not figured out how yet)
If I follow along with their api and use .then (as illustrated in the getRow) function, I am back in the same problem I was in before.
function checkRequest(id) {
console.log(id);
var deferred = Q.defer();
connection.query('SELECT * FROM teacher_request WHERE student_id ='+id, function(err, row){
deferred.resolve(row.length);
});
return deferred.promise;
}
var getRow = function(id){
checkRequest(id).then(function(val) {
console.log(val); // works great
return val; //back to the same problem
});
}
The roster needs to be able to be pulled from an external API which is why I am not bundling the request check with the original roster query.
Thanks in advance
From the stuff you posted, I assume you have not really understood the concept of promises. They allow you to queue up callbacks, that get executed, when the asynchronous operation has finished (by succeeding or failing).
So instead of somehow getting the results back to your synchronous workflow, you should convert that workflow to work asynchronous as well. So a small example for your current problem:
// your students' ids in here
var studentsArray = [ 1, 2, 5, 6, 9 ];
for( var i=0; i<studentsArray.length; i++ ) {
checkRequest( i )
.then( function( data ){
console.log( data.student_id );
// any other code related to a specific student in here
});
}
or another option, if you need all students' data at the same time:
// your students' ids in here
var studentsArray = [ 1, 2, 5, 6, 9 ];
// collect all promises
var reqs = [];
for( var i=0; i<studentsArray.length; i++ ) {
reqs.push( checkRequest( i ) );
}
Q.all( reqs )
.then( function(){
// code in here
// use `arguments` to access data
});
I am only getting back the first result in the array, and want to retrieve all the available results.
function runForm(){
$("#stock_news").html("");
var stockSymbol = $("input").val();
//very long str
var newsStocks = "http://query.yahooapis.com/v1/public/yql?
q=select%20*%20from%20html%20where%20url%3D'http%3A%2F%2Ffinance.yahoo.com
%2Fq%3Fs%3D"+stockSymbol+"'%20and%20xpath%3D'%2F%2Fdiv%5B%40id%3D%22yfi_headlines
%22%5D%2Fdiv%5B2%5D%2Ful%2Fli%2Fa'&format=json&diagnostics=true&callback=";
//getJSON
$.getJSON(newsStocks, function(data) {
var headlines = data.query.results.a[0];
//newsStr
newsStr = "<h3 style='text-decoration:underline'>Current Headlines</h3><p><ol>
<li><a href='"+headlines.href+"'>"+headlines.content+
"</a></li></ol></p>";
$("#stock_news").html(newsStr);
});
You haven't given enough information, but I could guess that this var headlines = data.query.results.a[0]; is your issue. It would seem like the other results are there, but you're filtering them out. console.log(data) and console.log(data.query.results) and look at what all is in there. Otherwise, update your question with more information.
Update:
This is a very basic ajax call (with jQuery) and a for loop to loop through and use each result.
$.get('path/here', function(data) {
//if your data is an array
for (var i=0; i<data.length; ++i) {
var item = data[i];
console.log(item);
}
});
Here's a live demo (click), but I'm not going to use the ajax data since the path is not valid.
Here's the same example, but using $.each. I prefer the for loop...why use jQuery for something so simple?
$.get('path/here', function(data) {
$.each(data, function(item, index) {
console.log(index);
});
});