We Keep Coding

Get specifics ids in IndexedDB [duplicate]

I want to execute this query
select * from properties where propertyCode IN ("field1", "field2", "field3")
How can I achieve this in IndexedDB
I tried this thing
getData : function (indexName, params, objectStoreName) {
var defer = $q.defer(),
db, transaction, index, cursorRequest, request, objectStore, resultSet, dataList = [];
request = indexedDB.open('test');
request.onsuccess = function (event) {
db = request.result;
transaction = db.transaction(objectStoreName);
objectStore = transaction.objectStore(objectStoreName);
index = objectStore.index(indexName);
cursorRequest = index.openCursor(IDBKeyRange.only(params));
cursorRequest.onsuccess = function () {
resultSet = cursorRequest.result;
if(resultSet){
dataList.push(resultSet.value);
resultSet.continue();
}
else{
console.log(dataList);
defer.resolve(dataList);
}
};
cursorRequest.onerror = function (event) {
console.log('Error while opening cursor');
}
}
request.onerror = function (event) {
console.log('Not able to get access to DB in executeQuery');
}
return defer.promise;
But didn't worked. I tried google but couldn't find exact answer.

If you consider that IN is essentially equivalent to field1 == propertyCode OR field2 == propertyCode, then you could say that IN is just another way of using OR.
IndexedDB cannot do OR (unions) from a single request.
Generally, your only recourse is to do separate requests, then merge them in memory. Generally, this will not have great performance. If you are dealing with a lot of objects, you might want to consider giving up altogether on this approach and thinking of how to avoid such an approach.
Another approach is to iterate over all objects in memory, and then filter those that don't meet your conditions. Again, terrible performance.
Here is a gimmicky hack that might give you decent performance, but it requires some extra work and a tiny bit of storage overhead:
Store an extra field in your objects. For example, plan to use a property named hasPropertyCodeX.
Whenever any of the 3 properties are true (has the right code), set the field (as in, just make it a property of the object, its value is irrelevant).
When none of the 3 properties are true, delete the property from the object.
Whenever the object is modified, update the derived property (set or unset it as appropriate).
Create an index on this derived property in indexedDB.
Open a cursor over the index. Only objects with a property present will appear in the cursor results.
Example for 3rd approach
var request = indexedDB.open(...);
request.onupgradeneeded = upgrade;
function upgrade(event) {
var db = event.target.result;
var store = db.createObjectStore('store', ...);
// Create another index for the special property
var index = store.createIndex('hasPropCodeX', 'hasPropCodeX');
}
function putThing(db, thing) {
// Before storing the thing, secretly update the hasPropCodeX value
// which is derived from the thing's other properties
if(thing.field1 === 'propCode' || thing.field2 === 'propCode' ||
thing.field3 === 'propCode') {
thing.hasPropCodeX = 1;
} else {
delete thing.hasPropCodeX;
}
var tx = db.transaction('store', 'readwrite');
var store = tx.objectStore('store');
store.put(thing);
}
function getThingsWherePropCodeXInAnyof3Fields(db, callback) {
var things = [];
var tx = db.transaction('store');
var store = tx.objectStore('store');
var index = store.index('hasPropCodeX');
var request = index.openCursor();
request.onsuccess = function(event) {
var cursor = event.target.result;
if(cursor) {
var thing = cursor.value;
things.push(thing);
cursor.continue();
} else {
callback(things);
}
};
request.onerror = function(event) {
console.error(event.target.error);
callback(things);
};
}
// Now that you have an api, here is some example calling code
// Not bothering to promisify it
function getData() {
var request = indexedDB.open(...);
request.onsuccess = function(event) {
var db = event.target.result;
getThingsWherePropCodeXInAnyof3Fields(db, function(things) {
console.log('Got %s things', things.length);
for(let thing of things) {
console.log('Thing', thing);
}
});
};
}

javascript function move to webworker

I have function:
function addModel() {
var values = new Array();
var $input = $('input[type=\'text\']');
var error = 0;
$input.each(function() {
$(this).removeClass('double-error');
var that = this;
if (that.value!='') {
values[that.value] = 0;
$('input[type=\'text\']').each(function() {
if (this.value == that.value) {
values[that.value]++;
}
});
}
});
$input.each(function(key) {
if (values[this.value]>1) {
//error++;
var name = this.value;
var product_model = $(this).parent().parent().find('.product-model').text();
var m = product_model.toLowerCase().areplace(search,replace);
$(this).parent().find('input[type=\'text\']').val(name + '-' + m);
}
});
return error <= 0; //return error > 0 ? false : true;
}
where are a lot of inputs to recheck... up to 50000. Usually are about 5000 to 20000 inputs. Of course browsers are freezing... How to move this function to web-worker and call it to get data back and fill form type="text"
thank you in advance.

Web workers don't have direct access to the DOM. So to do this, you'd need to gather the values of all 5-50k inputs into an array or similar, and then send that to the web worker (via postMessage) for processing, and have the web worker do the relevant processing and post the result back, and then use that result to update the inputs. See any web worker tutorial for the details of launching the worker and passing messages back and forth (and/or see my answer here).
Even just gathering up the values of the inputs and posting them to the web worker is going to take significant time on the main UI thread, though, as is accepting the result from the worker and updating the inputs; even 5k inputs is just far, far too many for a web page.

If maintaining browser responsiveness is the issue, then releasing the main thread periodically will allow the browser to process user input and DOM events. The key to this approach is to find ways to process the inputs in smaller batches. For example:
var INTERVAL = 10; // ms
var intervalId = setInterval((function () {
var values = [];
var $input = $('input[type=\'text\']');
var index;
return function () {
var $i = $input[index];
var el = $i.get();
$i.removeClass('double-error');
if (el.value != '') {
values[el.value] = 0;
$input.each(function() {
if (this.value == el.value) {
values[el.value]++;
}
});
}
if (index++ > $input.length) {
clearInterval(intervalId);
index = 0;
// Now set elements
intervalId = setInterval(function () {
var $i = $input[index];
var el = $i.get();
if (values[el.value] > 1) {
var name = el.value;
var product_model = $i.parent().parent().find('.product-model').text();
var m = product_model.toLowerCase().areplace(search,replace);
$i.parent().find('input[type=\'text\']').val(name + '-' + m);
}
if (index++ > $input.length) {
clearInterval(intervalId);
}
}, INTERVAL);
}
};
}()), INTERVAL);
Here, we do just a little bit of work, then use setInterval to release the main thread so that other work can be performed. After INTERVAL we will do some more work, until we finish and call clearInterval

Node/Javascript only send changed values

I'm writing a simple application where I send values to a mqtt broker given by a pot-meter (variable resistor). The thing I am trying to accomplish is that I only send changed values to save bandwidth. I am trying Object.observe, but that does not do anything. Can anybody help me?
My code:
var analogValue = 0;
every((0.5).second(), function() {
analogValue = my.sensor.analogRead();
var values = {values:[{key:'resistance', value: analogValue}]}
//another experiment here
var arr = ['resitance', analogValue];
Array.observe(arr, function(changes) {
console.log(changes);
});
arr[1] = analogValue
console.log('sent ',values,'to ',thingTopic)
client.publish(thingTopic, JSON.stringify(values));
});
var o = [analogValue];
Object.observe(o, function (changes) {
console.log(changes);
//eventually publish only changes to broker here
})
o.name = [analogValue]

You don't need to use Object.observe. You can just save the last measurement and check the new one against it. Like this:
// I'm assuming that any actual measurement will be different than 0
var lastMeasurement = 0;
every((0.5).second(), function() {
var analogValue = my.sensor.analogRead();
if (lastMeasurement !== analogValue) {
// the new value is different
var values = {values:[{key:'resistance', value: analogValue}]};
client.publish(thingTopic, JSON.stringify(values));
// update the last measurement value
lastMeasurement = analogValue;
}
});

javascript - get items with query and match items to a user who has favorited item

I am writing a script on parse.com's javascript cloud code SDK. Here is the information I have saved in my parse.com account and what I am trying to do with it.
I have a bunch of items saved in a parse class called TestItem, theses items have an objectId, item name, meal time (lunch, dinner) and a location for there columns. I also have a class called UserFavourites. In this class the objects have an objectId, item name and a pointer to the user who saved the item as a favourite.
And with this information I am trying to write a cloud code script in javascript. That will match the an item(s) to the item(s) that a user has favourited and send them a push notification saying where and what the item is and the location of the item. I have some code that will do that but this code will send a different notification for each item which could get annoying for the user here is that code.
Parse.Cloud.define("push", function(request, response) {
var TestItem = Parse.Object.extend("TestItem");
var query = new Parse.Query(TestItem);
query.limit(1000);
query.equalTo('school', 'Union College (NY)');
query.find({
success: function(resultsItem) {
//console.log("Successfully retrieved " + resultsItem.length + " :1111.");
for (var i = 0; i < resultsItem.length; i++) {
var object = resultsItem[i];
var item = object.get('item');
var school = object.get('school');
var meal = object.get('meal');
var meal = meal.toLowerCase();
var diningLocation = object.get('schoolMenu');
//var itemArray = [];
var UserFavourite = Parse.Object.extend("UserFavourite");
var queryFavourite = new Parse.Query(UserFavourite);
queryFavourite.limit(1000);
queryFavourite.equalTo("item", item)
queryFavourite.equalTo("school", school)
queryFavourite.find({
success: function(results) {
for (var i = 0; i < results.length; i++) {
var objectFav = results[i];
var user = objectFav.get('user');
var userID = user.id;
var realItem = objectFav.get('item');
console.log(objectFav.get('user'));
console.log(objectFav.get('item'));
var UserClass = Parse.Object.extend("User");
var queryUser = new Parse.Query(UserClass);
queryUser.get(userID, {
success: function(userResult) {
console.log(userResult.get('school'));
console.log('install:' + userResult.get('installation').id);
var userInstallationId = userResult.get('installation').id;
var queryInstallation = new Parse.Query(Parse.Installation);
queryInstallation.equalTo('objectId', userInstallationId);
queryInstallation.find({
success: function(results) {
console.log('number' + results.length);
Parse.Push.send({
// deviceType: [ "ios" ],
where: queryInstallation,
data: {
alert: realItem + " is being served at " + diningLocation + " for " + meal
}
},
{
success: function() {
// Push was successful
},
error: function(error) {
// Handle error
}
});
},
error: function(error) {
console.log('error');
}
});
},
error: function(error) {
console.log('error');
}
});
}
},
error: function(error) {
alert("Error: " + error.code + " " + error.message);
}
});
}
},
error: function(error) {
alert("Error: " + error.code + " " + error.message);
}
});
});
As you can see it is quite long and not very nice looking, I tried to save items to an array so to avoid sending two or more notifications but couldn't get that to work.
So I started writing another script that uses promises which looks much nicer but haven't gotten it all the way right now, it can match the items to users that have an item favourited and put the objectId's of those users in an array. Here is that code.
Parse.Cloud.define("test", function(request, response) {
var UserFavourite = Parse.Object.extend("UserFavourite");
var queryFavourite = new Parse.Query(UserFavourite);
var userArray = [];
var TestItem = Parse.Object.extend("TestItem");
var query = new Parse.Query(TestItem);
query.limit(1000);
query.equalTo('school', 'Union College (NY)');
query.find().then(function(results) {
return results;
}).then(function(results) {
var promises = [];
for (var i = 0; i < results.length; i++) {
var object = results[i];
var item = object.get('item');
var school = object.get('school');
var meal = object.get('meal');
var UserFavourite = Parse.Object.extend("UserFavourite");
var queryUser = new Parse.Query(UserFavourite);
queryUser.equalTo("item", item);
queryUser.equalTo("school", school);
var prom = queryUser.find().then(function(users) {
for (var i = 0; i < users.length; i++) {
var user = users[i];
var userID = user.get('user').id;
if (userArray.indexOf(userID) === -1) {
userArray.push(userID);
}
}
return userArray;
});
promises.push(prom);
}
return Parse.Promise.when.apply(Parse.Promise, promises);
}).then(function(results) {
console.log(userArray);
});
});
But now with this code I don't know where to go, I think using promises and such is the right way to go but I am now confused as once I have all the users that have an item favourited what to do, I then need to get there items that are favourited and are available in the TestItem class, this is where I am struggling.
Here is a pic of my UserFavourite class it has a pointer to the user who favorited the item as you can see, and also a user has more than one favorite.
Thanks a bunch for the help in advance.
Here is your code, and I changed a couple things.
Parse.Cloud.define("getAllFavoriteItems", function (request, response) {
var TestItems = Parse.Object.extend("TestItems");
var UserFavorites = Parse.Object.extend("UserFavorites");
var testItemsQuery = new Parse.Query(TestItems);
var userFavoritesQuery = new Parse.Query(UserFavorites);
testItemsQuery.equalTo('school', 'Union College (NY)');
userFavoritesQuery.include('testItems'); //This makes sure to pull all of the favorite item data instead of just the pointer object
userFavoritesQuery.matchesQuery('testItem', testItemsQuery); //This will run this second query against the TestItems
userFavoritesQuery.limit(1000); //limit results to 1000
userFavoritesQuery.ascending('userId'); //group the user id's together in your array
userFavoritesQuery.find({
success:function(results) {
var pushNotificationMessage = "";
var userId = "";
for (var i=0; i <results.length; i++) {
if (results[i].get('userId') != userId) {
if (results[i].get('userId') != "") {
//TODO send push notification
}
userId = results[i].get('userId');
pushNotificationMessage = ""; //start a new push notification
}
pushNotificationMessage += results[i].get('item').get('name') + ": " + results[i].get('item').get('location') + "\n";
//SOMEWHERE BEFORE HERE I NEED THE INSTALLATION ID OF THE USER
//TO SEND THE PUSH TO THAT USER
Parse.Push.send({
// deviceType: [ "ios" ],
where: queryInstallation,
data: {
alert: pushNotificationMessage
}
},
{
success: function() {
// Push was successful
},
error: function(error) {
// Handle error
}
});
}
response.success(true);
},
error:function(error) {
response.error();
}
})
});
Some code that might create push per user, rough outline though
if (i > 0) {
if (results[i].get('user') === results[i-1].get('user')) {
userItems.push(results[i]);
}
else {
userItems.length = 0;
}
}
else {
userItems.push(results[i]);
}
Not sure let me know if you understand what I'm trying to do...
So it a user has two items favourited I want it to group that into one, phrase that says what and where both items are being served
And here is code to send push
Parse.Push.send({
// deviceType: [ "ios" ],
where: queryInstallation,
data: {
alert: pushNotificationMessage
}
},
{
success: function() {
// Push was successful
},
error: function(error) {
// Handle error
}
});
It can also be done with then/ promises,

I agree with #Maxwell that your UserFavorite should have links to both User and TestItem. This makes it possible to make your cloud-function as simple as:
Parse.Cloud.define("getAllFavoriteItems", function(request, response) {
var TestItem = Parse.Object.extend("TestItem");
var UserFavorites = Parse.Object.extend("UserFavorites");
var testItemsQuery = new Parse.Query(TestItem);
var userFavoritesQuery = new Parse.Query(UserFavorites);
testItemsQuery.equalTo('school', request.params.school);
userFavoritesQuery.include('testItem');
userFavoritesQuery.include('user');
userFavoritesQuery.matchesQuery('testItem', testItemsQuery); //This will run this second query against the TestItems
userFavoritesQuery.find().then(function(results) {
var alerts = {};
for(var i =0 ; i<results.length; i++ ){
var user = results[i].get('user');
var testItem = results[i].get('testItem');
if(user && testItem){
var instId = user.get('installationId');
if(!alerts[instId]) {
alerts[instId] = [];
}
var m = results[i].get('item') + " is being served at {{diningLocation}} for " + testItem.get('meal');
alerts[instId].push(m);
}
}
response.success(alerts);
}, function(error) {
response.error();
});
});
This is working code that you can also find in my github repo.
You can also see the working demo here
The idea is the same as in Maxwell's answer: to have link in UserFavorites class to both User (where installationId is located) and TestItem entities. I've just made it working by including user and testItems properties in query, so when the result is returned filtered by school name I already have a list of installationIds.
Here is my schema:
User
TestItem
UserFavorites
Update:
In this code I added push notifications:
Parse.Cloud.define("getAllFavoriteItems", function(request, response) {
var TestItem = Parse.Object.extend("TestItem");
var UserFavorites = Parse.Object.extend("UserFavorites");
var testItemsQuery = new Parse.Query(TestItem);
var userFavoritesQuery = new Parse.Query(UserFavorites);
testItemsQuery.equalTo('school', request.params.school);
function SendPush(installationId, msg) {
var query = new Parse.Query(Parse.Installation);
query.equalTo('objectId', installationId);
Parse.Push.send({
where: query,
data: {alert: msg}
});
}
userFavoritesQuery.include('testItem');
userFavoritesQuery.include('user');
userFavoritesQuery.matchesQuery('testItem', testItemsQuery); //This will run this second query against the TestItems
userFavoritesQuery.find().then(function(results) {
var groupedAlerts = {};
// manually iterating though results to get alert strings ang group by user in groupedAlerts[installationId]
for(var i =0 ; i<results.length; i++ ){
var user = results[i].get('user');
var testItem = results[i].get('testItem');
if(user && testItem){
var instId = user.get('installationId');
if(!groupedAlerts[instId]) {
groupedAlerts[instId] = [];
}
var m = results[i].get('item') + " is being served at {{dining Location}} for " + testItem.get('meal');
groupedAlerts[instId].push(m);
}
}
// reformat to array and send push notifications
var alerts = [];
for(var key in groupedAlerts) {
alerts.push({
installationId: key,
alerts: groupedAlerts[key],
});
// Send push notifications
SendPush(key, groupedAlerts[key].join());
}
response.success(alerts);
}, function(error) {
response.error();
});
});
I've also updated test data in live demo (just press Get Alerts) or feel free to play around with test data hot it changes cloud code response. gitnub repo is also up to up to date.

This is based on what I understand as the problem you're trying to solve. If it's not addressing the right issue, let me know and I'll see what I can do.
Looking first at your database model, we can simplify this a bit by modifying the UserFavorites table. Starting with the initial two classes, you have a table of items and a table of users. Since a user can favorite many items and an item can be favorited by many users, we have a many-to-many relationship that exists. When this happens, we need to make a third class that points to each of the other two classes. This is where the UserFavorites table comes into play. In Parse terms, the UserFavorites table needs to have two pointers in it: one for the user and one for the item.
Once the UserFavorite table exists with it's two pointers, we can do a few things fairly easily. In your case, we have a few searching criteria:
each item must be at a given school
you want to limit your responses to the first 1000
To accomplish this you can combine two queries into one by calling matchesQuery.
Parse.Cloud.define("getAllFavoriteItems", function (request, response) {
var TestItems = Parse.Object.extend("TestItems");
var UserFavorites = Parse.Object.extend("UserFavorites");
var testItemsQuery = new Parse.Query(TestItems);
var userQuery = new Parse.Query(Parse.User);
var userFavoritesQuery = new Parse.Query(UserFavorites);
testItemsQuery.equalTo('school', 'Union College (NY)');
userQuery.include('Installation');
userFavoritesQuery.include('testItems'); //This makes sure to pull all of the favorite item data instead of just the pointer object
userFavoritesQuery.include('User'); //This makes sure to pull all of the favorite item data instead of just the pointer object
userFavoritesQuery.matchesQuery('testItem', testItemsQuery); //This will run this second query against the TestItems
userFavoritesQuery.matchesQuery('user', userQuery); //This will run the third query against Users, bringing the installation data along with it
userFavoritesQuery.limit(1000); //limit results to 1000
userFavoritesQuery.ascending('userId'); //group the user id's together in your array
userFavoritesQuery.find({
success:function(results) {
...
},
error:function(error) {
response.error();
}
})
})
Once we get that far, then compiling the push message for each user should be a matter of straight-forward string parsing logic. For example, in the success function, one way we can extract the data we is this:
success:function(results) {
var pushNotificationMessage = "";
var userId = "";
for (var i=0; i <results.length; i++) {
if (results[i].get('userId') != userId) {
if (results[i].get('userId') != "") {
//TODO send push notification
}
userId = results[i].get('userId');
pushNotificationMessage = ""; //start a new push notification
}
pushNotificationMessage += results[i].get('item').get('name') + ": " + results[i].get('item').get('location') + "\n";
}
response.success(true);
}
I haven't tested these examples to see if they'll work, but I hope this gives you an idea of how to simplify your queries into something a little more manageable.

Simpy cannot iterate over javascript object?

I have scoured the other question/answer for this and implemented everything and I still cannot access the values of the object. Here's the code I am using:
function apply_voucher(voucher) {
var dates = $.parseJSON($("[name='dates']").val());
var voucher_yes_no = new Array();
var voucher_reduction = new Array();
if(voucher.length > 0)
{
$.each(dates, function(room_id, these_dates) {
$.post('/multiroom/check_voucher/'+voucher+'/'+room_id, function(result) {
if(result.result == 'ok') {
voucher_yes_no.push('yes');
voucher_reduction.push(result.voucher_reduction);
} else {
voucher_yes_no.push('no');
}
}, 'json');
});
// check if there are any yes's in the array
if('yes' in voucher_yes_no) {
console.log("no yes's");
} else {
console.log(voucher_reduction);
console.log(typeof voucher_reduction);
for (var prop in voucher_reduction) {
console.log(prop);
console.log(voucher_reduction[prop]);
if (voucher_reduction.hasOwnProperty(prop)) {
console.log("prop: " + prop + " value: " + voucher_reduction[prop]);
}
}
}
}
}
Apologies for the constant console logging - I'm just trying to track everything to make sure it's all doing what it should. The console output I get from this is below:
...which shows the object containing one value, "1.01" and my console.log of the typeof it to make sure it is actually an object (as I thought I was going mad at one point). After this there is nothing from inside the for-in loop. I have tried jquery's $.each() also to no avail. I can't understand why nothing I'm trying is working!

It does not work because the Ajax call is asynchronous!
You are reading the values BEFORE it is populated!
Move the code in and watch it magically start working since it will run after you actually populate the Array!
function apply_voucher(voucher) {
var room_id = "169";
var dates = $.parseJSON($("[name='dates']").val());
var voucher_reduction = new Array();
$.post('/multiroom/check_voucher/'+voucher+'/'+room_id, function(result) {
if(result.result == 'ok') {
voucher_reduction.push(result.voucher_reduction);
}
console.log(voucher_reduction);
console.log(typeof voucher_reduction);
for (var prop in voucher_reduction) {
console.log(prop);
console.log(voucher_reduction[prop]);
if (voucher_reduction.hasOwnProperty(prop)) {
console.log("prop: " + prop + " value: " + voucher_reduction[prop]);
}
}
}, 'json');
}
From what it looks like, you plan on making that Ajax call in a loop. For this you need to wait for all of the requests to be done. You need to use when() and then(). It is answered in another question: https://stackoverflow.com/a/9865124/14104

Just to say for future viewers that changing the way I did this to use proper deferred objects and promises, which blew my head up for a while, but I got there! Thanks for all the help, particularly #epascarello for pointing me in the right direction :) As soon as I started doing it this way the arrays began behaving like arrays again as well, hooray!
Here's the final code:
function apply_voucher(voucher) {
var booking_id = $("[name='booking_id']").val();
var dates = $.parseJSON($("[name='dates']").val());
if(voucher.length > 0) {
var data = []; // the ids coming back from serviceA
var deferredA = blah(data, voucher, dates); // has to add the ids to data
deferredA.done(function() { // if blah successful...
var voucher_yes_no = data[0];
var voucher_reduction = data[1];
if(voucher_yes_no.indexOf("yes") !== -1)
{
console.log("at least one yes!");
// change value of voucher_reduction field
var reduction_total = 0;
for(var i = 0; i < voucher_reduction.length; i++) {
reduction_total += voucher_reduction[i];
}
console.log(reduction_total);
}
else
{
console.log("there are no yes's");
}
});
}
}
function blah(data, voucher, dates) {
var dfd = $.Deferred();
var voucher_yes_no = new Array();
var voucher_reduction = new Array();
var cycles = 0;
var dates_length = 0;
for(var prop in dates) {
++dates_length;
}
$.each(dates, function(room_id, these_dates) {
$.post('/multiroom/check_voucher/'+voucher+'/'+room_id, function(result) {
if(result.result == 'ok') {
voucher_reduction.push(result.voucher_reduction);
voucher_yes_no.push('yes');
} else {
voucher_yes_no.push('no');
}
++cycles;
if(cycles == dates_length) {
data.push(voucher_yes_no);
data.push(voucher_reduction);
dfd.resolve();
}
}, 'json');
});
return dfd.promise();
}

Can you show how voucher_reduction is defined?
I am wondering where the second line of the debug output comes from, the one starting with '0'.

in this line:
console.log(vouncher_reduction[prop]);
^
The name of the variable is wrong (then) and probably that is breaking your code.

I think there are no problem with your loop.
But perhaps with your object.
Are you sure what properties has enumerable ?
Try to execute this to check :
Object.getOwnPropertyDescriptor(voucher_reduction,'0');
If it return undefined, the property was not exist.