I've been working on node.js for a short time and currently have the following problem: I would like to iterate through an array and send an http request for each element in the array. These requests should be executed every 5 seconds. In addition to this, this should be done max. 10 times.
That means every 5 seconds an http request should be sent for all elements in the array.
I have already tried a branched async for and for each loop, but I am not getting the desired result.
I know where the problem is with my code but can't find another solution.
It looks something like this:
// Set for loop
for (var i = 0; i <= 10; i++) {
setTimeout(function () {
// Iterate through every element within the array
sendItems.forEach(function (arrayItem) {
// Some code
request (.....)
// Exit condition
if (sendItems[sendItems.length - 1].status === 'Failed'|||
sendItems[sendItems.length - 1].status ==='Successful') {
if (cbFlag === false) {
interval = 0;
resolve(sendItems);
}
}
});
}interval * i);
Assuming by request you're referring to the nodejs module. Here a possible solution using something strange like a sleep :)
const request = require('request');
const _request = require('util').promisify(request);
let sendItems = [1,2,3];
let sleep = (ms) => {
return new Promise(function (resolve, reject) {
setTimeout(function () {
console.log(`waiting ${ms/1000} sec..`)
resolve();
}, ms);
})
}
(async function loop() {
for (let i = 0; i < 10; i++) {
for (let id of sendItems) {
let r = await _request('https://jsonplaceholder.typicode.com/posts/'+id, { json: true })
console.log(r.body.id);
}
await sleep(5000);
} console.log("ok that's it")
})();
Related
In my angular app, I have 2 methods save() and saveTriggers(). saveTriggers() updates all records by calling a web service (C#). I want to make sure that a block of code is executed after all records are updated in saveTriggers() and control is returned to save(). I believe I need to pass something from the saveTriggers() to make finally block execute. I tried various things, nothing works. Using .then() also gives the same error. I am not that good at JS. Can you please guide me.
vm.updatedTriggers = []; // IDs are pushed in
vm.saveTriggers = function () {
if (vm.updatedTriggers.length === 0) {
vm.close();
} else {
vm.saving = true;
vm.save()
.finally(function () { // ERROR - Cannot read property 'finally' of undefined
console.log("Saved all. Closing..."); // Never REACHES here
vm.saving = false;
vm.updated = true;
$uibModalInstance.close(true);
});
}
};
vm.save = function () {
//vm.saving = true;
for (var i = 0; i < vm.updatedTriggers.length; i++) {
var trigger = vm.triggers.find(t => t.id === vm.updatedTriggers[i]);
var input = {
id: trigger.id,
target: trigger.target,
targetInfo: vm.targetData,
event: trigger.event,
eventQuantity: trigger.eventQuantity,
eventQuantityExtra: trigger.eventQuantityExtra
};
rpmService.editDeviceTrigger(input);
/*.finally(function () {
console.log("Updated event"); // Reaches here
vm.updated = true;
return Promise.resolve(2);
});*/ // Commenting this also doesn't help
}
return Promise.resolve(2);
};
rpmService.editDeviceTrigger(input)
public async Task EditDeviceTrigger(EditDeviceTriggerInput input) {
// calls other methods with await
// Doesn't return anything
}
EDIT: Updated Code: I got rid of the error, but the output is not is expected series.
vm.saveTriggers = function () {
vm.saving = true;
vm.save().then
(function success() {
console.log("Returned Result ");
console.log("Saved all. Closing..."); // These lines are executed before the event is upated
vm.saving = false;
$uibModalInstance.close(true);
});
};
vm.save = function () {
var deferred = $q.defer();
for (var i = 0; i < vm.updatedTriggers.length; i++) {
var trigger = vm.triggers.find(t => t.id === vm.updatedTriggers[i]);
var input = {
id: trigger.id,
....
};
rpmService.editDeviceTrigger(input)
.finally(function () {
console.log("Updated event"); // Successfully updates all events
vm.updated = true;
});
}
deferred.resolve();
return deferred.promise;
};
OUTPUT:
Returned Result
Saved all. Closing...
Updated event
EXPECTED OUTPUT:
Updated event
Returned Result
Saved all. Closing...
Thanks.
Usually you dont need $q.defer-related things, but u can do same using it if u want.
Here I guess you just need to collect all your save promises and return new resulting one using $q.all:
vm.save = function () {
const myAwesomePromises = []
for (var i = 0; i < vm.updatedTriggers.length; i++) {
...
const savePromise = rpmService.editDeviceTrigger(input);
savePromise.finally(() => console.log('edit device finally'));// <-- not sure u need this
myAwesomePromises.push(savePromise);
}
return $q.all(myAwesomePromises).finally(() => console.log('All edit device finally'));
};
I am working on a system that currently requires me to load all items from an API.
The API is built with pagination feature in it. I keep calling the API a number of times and $http.get cursing the system not to respond. For example, once I load the page that needs to call the API many times (like 50 to 80 times depending on the number of pages), for a few minutes anything I do won't respond until the calling of the API is almost finished. I already tried a lot of ways but it won't work.
$scope.loadAllPagedItems = function (category_uuid, max_pageitem, item_perpage) {
for (var a = 0 ; a < max_pageitem; a++) {
itemResource.findItems(category_uuid, item_perpage, a).then(function (response) {
if (response.data.data.length > 0) {
for (var a = 2 ; a < $scope.categories.length; a++) {
if ($scope.categories[a][0].category_uuid == response.data.data[0].category_uuid) {
for (var j = 0; j < response.data.data.length; j++) {
$scope.categories[a][0].data.push(response.data.data[j]);
}
}
}
}
}, function (error) {
console.log(error);
})
}
}
Is there any way I can do this better?
Sequentially Retrieving Paginated Data from an Asynchronous API
$scope.loadAllPagedItems = function(category_uuid, max_pageitem, item_perpage) {
var promise = $q.when([]);
for (let a = 0 ; a < max_pageitem; a++) {
promise = promise
.then(function(dataArray) {
var p = itemResource.findItems(category_uuid, item_perpage, a);
p = p.then(function (response) {
return dataArray.concat(response.data.data);
});
return p;
});
};
return promise;
};
The above example, executes XHRs sequentially and uses the array concat method to merge the resolved arrays into a single array.
Usage:
$scope.loadAllPagedItems(category, pages, itemsPerPages)
.then(function(finalArray) {
console.log(finalArray);
}).catch(function(response) {
console.log("ERROR ",response.status);
throw response;
});
I am trying to make a node express app where I fetch data from different url's making a call to node-fetch to pull the body of some pages and other information about certain url endpoints. I want to then render a html table to display this data through an array of information. I am having trouble with the call to render the information as all the functions are asynchronous making it difficult to make sure all the promise calls have been resolved before making my call to render the page. I have been looking into using bluebird and other promise calls of .finally() and .all() but they don't seem to work on my data as it is not an array of promise calls, but an array of objects. Each object was 4 promise calls to fetch data relating to a column of my table all in one row. Is there a function or specific way to render the page after all promises are resolved?
var express = require('express');
var fetch = require('node-fetch');
fetch.Promise = require('bluebird');
var router = express.Router();
const client = require('../platform-support-tools');
function makeArray() {
var registry = client.getDirectory();
var data_arr = [];
for (var i = 0; i < registry.length; i++) {
var firstUp = 0;
for (var j = 0; i < registry[i]; j++) {
if (registry[i][j]['status'] == 'UP') {
firstUp = j;
break;
}
}
var object = registry[i][firstUp];
data_arr.push({
'name': object['app'],
'status': object['status'],
'swagUrl': object['homePageUrl'] + 'swagger-ui.html',
'swag': getSwag(object),
'version': getVersion(object['statusPageUrl']),
'timestamp': getTimestamp(object['statusPageUrl']),
'description': getDescription(object['healthCheckUrl'])
});
}
return data_arr;
}
function getSwag(object_in) {
var homeUrl = object_in['homePageUrl'];
if (homeUrl[homeUrl.length - 1] != '/'){
homeUrl += '/';
}
var datum = fetch(homeUrl + 'swagger-ui.html')
.then(function (res) {
return res.ok;
}).catch(function (err) {
return 'none';
});
return datum;
}
function getVersion(url_in) {
var version = fetch(url_in)
.then(function(res) {
return res.json();
}).then(function(body) {
return body['version'];
}).catch(function (error) {
return 'none';
});
return version;
}
function getTimestamp(url_in) {
var timestamp = fetch(url_in)
.then(function(res) {
return res.json();
}).then(function(body) {
return body['timestamp'];
}).then(function (res) {
return body['version'];
}).catch(function (error) {
return 'none';
});
return timestamp;
}
function getDescription(url_in) {
var des = fetch(url_in)
.then(function(res) {
return res.json();
}).then(function(body) {
return body['description'];
}).catch(function (error) {
return 'none';
});
return des;
}
/* GET home page. */
router.get('/', function (req, res, next) {
var data_arr = makeArray();
Promise.all(data_arr)
.then(function (response) {
//sorting by app name alphabetically
response.sort(function (a, b) {
return (a.name > b.name) ? 1 : ((b.name > a.name) ? -1 : 0);
});
res.render('registry', {title: 'Service Registry', arr: response})
}).catch(function (err) {
console.log('There was an error loading the page: '+err);
});
});
To wait on all those promises, you will have to put them into an array so you can use Promise.all() on them. You can do that like this:
let promises = [];
for (item of data_arr) {
promises.push(item.swag);
promises.push(item.version);
promises.push(item.timestamp);
promises.push(item.description);
}
Promise.all(promises).then(function(results) {
// all promises done here
})
If you want the values from all those promises, back into the object that's a bit more work.
let promises = [];
for (item of data_arr) {
promises.push(item.swag);
promises.push(item.version);
promises.push(item.timestamp);
promises.push(item.description);
}
Promise.all(promises).then(function(results) {
// replace promises with their resolved values
let index = 0;
for (let i = 0; i < results.length; i += 4) {
data_arr[index].swag = results[i];
data_arr[index].version = results[i + 1];
data_arr[index].timestamp = results[i + 2];
data_arr[index].description = results[i + 3];
++index;
});
return data_arr;
}).then(function(data_arr) {
// process results here in the array of objects
});
If you had to do this more often that just this once, you could remove the hard coding of property names and could iterate all the properties, collect the property names that contain promises and automatically process just those.
And, here's a more general version that takes an array of objects where some properties on the objects are promises. This implementation modifies the promise properties on the objects in place (it does not copy the array of the objects).
function promiseAllProps(arrayOfObjects) {
let datum = [];
let promises = [];
arrayOfObjects.forEach(function(obj, index) {
Object.keys(obj).forEach(function(prop) {
let val = obj[prop];
// if it smells like a promise, lets track it
if (val && val.then) {
promises.push(val);
// and keep track of where it came from
datum.push({obj: obj, prop: prop});
}
});
});
return Promise.all(promises).then(function(results) {
// now put all the results back in original arrayOfObjects in place of the promises
// so now instead of promises, the actaul values are there
results.forEach(function(val, index) {
// get the info for this index
let info = datum[index];
// use that info to know which object and which property this value belongs to
info.obj[info.prop] = val;
});
// make resolved value be our original (now modified) array of objects
return arrayOfObjects;
});
}
You would use this like this:
// data_arr is array of objects where some properties are promises
promiseAllProps(data_arr).then(function(r) {
// r is a modified data_arr where all promises in the
// array of objects were replaced with their resolved values
}).catch(function(err) {
// handle error
});
Using the Bluebird promise library, you can make use of both Promise.map() and Promise.props() and the above function would simply be this:
function promiseAllProps(arrayOfObjects) {
return Promise.map(arrayOfObjects, function(obj) {
return Promise.props(obj);
});
}
Promise.props() iterates an object to find all properties that have promises as values and uses Promise.all() to await all those promises and it returns a new object with all the original properties, but the promises replaced by the resolved values. Since we have an array of objects, we use Promise.map() to iterate and await the whole array of those.
I'm trying to copy the data from firebase to an array using angular 2. But i'm unable to push the data into the array.
Here's the code:
Variables:
uid: string = '';
agencyItems: FirebaseListObservable<any[]>;
trackerItems: FirebaseListObservable<any[]>;
agencyID: any[] = [];
getData()
this.af.auth.subscribe(auth => {
if (auth) {
this.uid = auth.auth.uid;
}
});
this.getAgencyData();
console.log("AgentID: ",this.agencyID);
console.log("Array Length = ",this.agencyID.length); //PROBLEM HERE: Array agencyID is still 0.
this.getTrackerData();
getAgencyData():
console.log("Fetching agency data");
this.agencyItems = this.af.database.list('/agencies/',{preserveSnapshot:true});
this.agencyItems.subscribe(snapshots => {
snapshots.forEach(snapshot => {
console.log(snapshot.val()._id);
this.agencyID.push(snapshot.val()._id);
});
});
getTrackerData():
for (let i = 0; i < this.agencyID.length; i++)
{
console.log("Fetching Tracker data");
this.trackerItems = this.af.database.list('/tracker/' + this.agencyID[i]);
this.trackerItems.subscribe(trackerItems => trackerItems.forEach(Titem =>
console.log("Tracker name: " + Titem.name),
));
}
Here is the debug console screenshot:
Since i'm a newbie to web programming some code may seem completely unnecessary.
What am I doing wrong in this code? How can I implement the same.
The problem is the location where, or better WHEN, you are checking the length of the array. You make an asynchronous call when you fetch the data, but you are checking the length of the array before the data has been returned. Therefore the array is still empty.
Try the following in getAgencyData():
console.log("Fetching agency data");
this.agencyItems = this.af.database.list('/agencies/',{preserveSnapshot:true});
this.agencyItems.subscribe(snapshots => {
snapshots.forEach(snapshot => {
console.log(snapshot.val()._id);
this.agencyID.push(snapshot.val()._id);
console.log("Array Length = ",this.agencyID.length); // See the length of the array growing ;)
});
// EDIT
this.getTrackerData();
});
I'm making an AJAX request for each item in a loop, the end REST service can only perform one request at a time so I need the loop to wait for each request to complete before continuing with the next. How do I do this?
For reference, the end service is performing update tasks on DynamoDB tables - only one table can be modified at once hence my requirement to wait until I get a response before continuing. I could send them all to the server in one hit and handle there, although that makes it hard to receive feedback when each update is completed.
angular.forEach($scope.someArray,
function (value) {
var postdata = {
bla: value
};
$http.post('/some_url', postdata)
.then(
function(result) {
console.log("Success.");
},
function(data) {
console.log("Failure.");
}
);
}
);
Do you really need the forEach? I would not use it and go for something like that:
function req(arr) {
if (angular.isArray(arr) && arr.length > 0) {
var postdata = {
bla: arr[0]
};
$http.post('/some_url', postdata)
.then(
function(result) {
console.log("Success.");
arr.shift();
req(arr);
},
function(data) {
console.log("Failure.");
// if you want to continue even if it fails:
//arr.shift();
//req(arr);
}
);
}
}
req($scope.someArray);
If you really must make one request at a time (are you sure there isn't a more efficient alternative?), then you'll have to use something other than Angular.forEach.
What about something like this (you will need to inject $q):
function doWhateverWithAll(someArray) {
// Mark which request we're currently doing
var currentRequest = 0;
// Make this promise based.
var deferred = $q.deferred();
// Set up a result array
var results = []
function makeNextRequest() {
// Do whatever you need with the array item.
var postData = someArray[currentRequest].blah;
$http.post('some/url', postData)
.then( function (data){
// Save the result.
results.push(data);
// Increment progress.
currentRequest++;
// Continue if there are more items.
if (currentRequest < someArray.length){
makeNextRequest();
}
// Resolve the promise otherwise.
else {
deferred.resolve(results);
}
});
// TODO handle errors appropriately.
}
// return a promise for the completed requests
return deferred.promise;
}
Then, in your controller/service, you can do the following:
doWhateverWithAll($scope.someArray)
.then(function(results){
// deal with results.
});