Develop Reference

Return books that contain specific genres

I want to retrieve the object that contains specific genres based on show variable value
const books=
"genres" : [
"history"
],
"title" : "Yemen",
"published" : NumberInt(1990),
"author" : ObjectId("5ef5fb84b368d90d48e785a1"),
},{"genres" : [
"Web",
"Programming",
"Development"
],
"title" : "JavaScript for Profissional",
"published" : NumberInt(2016),
"author" : ObjectId("5f046ddc4a55f425d86311d0"),},
{"genres" : ["Programming"],
"title" : "CSS for Profissional",
"published" : NumberInt(2019),
"author" : ObjectId("5f046ddc4a55f425d86311d0"),
}
This is the books object.
I want to get the books that contain specific genres
like that
const show="programming"
const booksToShow =
show === "All"
? books
: books.filter((book) => book.genres.map(g=>{
if(g.toLocaleLowerCase()===showAll.toLocaleLowerCase())
return book
}
)
everything executed perfectly but it doesn't return any value into booksToShow while it supposed to return this object
{"genres" : [
"Web",
"Programming",
"Development"
],
"title" : "JavaScript for Profissional",
"published" : NumberInt(2016),
"author" : ObjectId("5f046ddc4a55f425d86311d0"),}
so are there anyway to repair this problem

The second part of your ternary condition can work using some to know if your books contains at least the given genre once :
books.filter(book => book.genres.some(g => g.toLocaleLowerCase() === show.toLocaleLowerCase()))
I have some performance concerns about this solution though. You may want to apply toLocaleLowerCase() to all books either once the data is received or directly within your database to avoid doing this operation every time your component re-renders.
By doing so you will be able to replace some by includes, drastically improving your perfs:
books.filter(book => book.genres.includes(show))

Solution with a double filter:
const books= [{
"genres" : [
"history"
],
"title" : "Yemen",
"published" : 1990,
"author" : "5ef5fb84b368d90d48e785a1"
},{"genres" : [
"Web",
"Programming",
"Development"
],
"title" : "JavaScript for Profissional",
"published" : 2016,
"author" : "5f046ddc4a55f425d86311d0"
},
{"genres" : ["Programming"],
"title" : "CSS for Profissional",
"published" : 2019,
"author" : "5f046ddc4a55f425d86311d0",
}];
const show="programming".toUpperCase();
const booksToShow = show === "All" ? books : books.filter((b) =>
b.genres.filter((g) =>
g.toUpperCase() === show
).length > 0);
console.log(booksToShow);

Find nested property from ember lodash and pick the value

I am new to javascript.
I would like to check whether the specific nested property is present or not in an array of items, ex)
[{
"_id" : ObjectId("5c4ec057e21b840001968d31"),
"status" : "ACTIVE",
"customerId" : "sample-book",
"bookInfo" : {
"bookChunks" : [
{
"key" : "Name",
"value" : "test"
},
{
"key" : "Surname1",
"value" : "testtt"
},
{
"key" : "user-contact",
"value" : "sample-value",
"ContactList" : {
"id" : "sample-id",
"timeStamp" : "Tue, 20 Sep 2016 07:49:25 +0000",
"contacts" : [
{
"id" : "contact-id1",
"name" : "Max Muller",
"phone_number" : "+XXXXXXX"
},
{
"id" : "contact-id2",
"name" : "Max Muller",
"phone_number" : "+XXXXXXX"
}
]
}
}
]
}
},
{
"_id" : ObjectId("5c4ec057e21b840001968d32"),
"status" : "ACTIVE",
"customerId" : "sample-book1",
"bookInfo" : {
"bookChunks" : [
{
"key" : "Name",
"value" : "test"
},
{
"key" : "Surname1",
"value" : "testtt"
}
]
}
}]
Here, I would like to find whether any item has ContactList or contacts present. If it is present take the item and put it in a separate list.
I am using ember-lodash. Using normal javascript or lodash would be fine for me. Any help will be really appreciated.

You could use filter and some. This returns all the objects which have at least one object with ContactList property inside bookInfo.bookChunks array.
const input=[{"_id":"5c4ec057e21b840001968d31","status":"ACTIVE","customerId":"sample-book","bookInfo":{"bookChunks":[{"key":"Name","value":"test"},{"key":"Surname1","value":"testtt"},{"key":"user-contact","value":"sample-value","ContactList":{"id":"sample-id","timeStamp":"Tue, 20 Sep 2016 07:49:25 +0000","contacts":[{"id":"contact-id1","name":"Max Muller","phone_number":"+XXXXXXX"},{"id":"contact-id2","name":"Max Muller","phone_number":"+XXXXXXX"}]}}]}},{"_id":"5c4ec057e21b840001968d32","status":"ACTIVE","customerId":"sample-book1","bookInfo":{"bookChunks":[{"key":"Name","value":"test"},{"key":"Surname1","value":"testtt"}]}}]
const output = input.filter(o =>
o.bookInfo.bookChunks.some(c => "ContactList" in c)
)
console.log(output)
If you just want to check if any of the objects have ContactList, you could replace filter with another some
(Note: This assumes that bookInfo.bookChunks will not be undefined. Otherwise you'd have to add a undefined check before using the nested property)

Mongoose find returns document instead of specific object in array

When I try to find specific object in array using find({query}) I always get all elements from array.
Activities array stores activities (it would be a thousands of them) as you can see in the following snippet:
This is my collection:
{
"_id" : ObjectId("58407140755324d04db2ce95"),
"owner" : 103429326776572,
"activities" : [
{
"name" : "test1",
"startTime" : ISODate("2016-08-11T17:41:54Z"),
"type" : "te1",
"lat" : 1,
"lon" : 1,
"creator" : 126212904493088,
"coverPhoto" : {
"name" : "test1",
"path" : "c:\\Users\\Francis\\Desktop\\dusk\\public\\coverPhotos\\SJ9tpP6Mx.jpg"
},
"identifier" : "H1g9F6vpGl",
"users" : [
1,
2,
3
],
"hashTags" : [
"some",
"hashtags"
]
},
{
"name" : "test2",
"startTime" : ISODate("2016-08-11T17:41:53Z"),
"type" : "te2",
"lat" : 1,
"lon" : 1,
"creator" : 103312904493090,
"coverPhoto" : {
"name" : "test2",
"path" : "c:\\Users\\Francis\\Desktop\\dusk\\public\\coverPhotos\\Hy8qpvafe.jpg"
},
"identifier" : "rJlU5TvpMx",
"users" : [
1,
2,
3
],
"hashTags" : [
"some",
"hashtags"
]
}
]
}
I need to get for example an activity that has specific identifier.
I tried to use queries like:
1) db.myCollection.find({'activities.identifier' : "rJlU5TvpMx"})
2) db.myCollection.find({'activities' : { $elemMatch : { "identifier" : "rJlU5TvpMx", "creator" : 103312904493090 } })
And all combinations with '' or "" signs
I found above queries at mongodb docs in equal documents schema as mine is.
Can you tell me what am I doing wrong ?

You can try either use single match or multiple match based on your need. This makes use of $elemMatch(projection)
db.myCollection.find({"_id" : ObjectId("58407140755324d04db2ce95")},
{activities: {$elemMatch: { identifier: "rJlU5TvpMx"}}})
db.myCollection.find( {"_id" : ObjectId("58407140755324d04db2ce95")},
{activities: {$elemMatch: {creator : 103312904493090, identifier: "rJlU5TvpMx" }}})

You are looking for the projection object which gets passed as an argument in your query. It allows the return of specific fields from your search rather than the entire document. http://mongoosejs.com/docs/api.html#model_Model.find
I would also suggest looking at the response to this question here: Mongoose Query: Find an element inside an array which makes use of the unwind operator to enter the array as it seems to be relevant to your needs.

In the collection you are searching in, you have just one Document(Object). If you apply method find() to your collection and the query inside matches the value in activities.identifier it will return the only Document(object).
To have a better understanding of what I am talking about check example on mongoose API doc
And query result here.
Try check this out https://docs.mongodb.com/v3.0/reference/operator/projection/elemMatch/#proj._S_elemMatch instead

Query to Match on nth Document of an Array

I am new to MongoDB and I am doing some exercises on it. In particular I got stuck on this exercise, of which I report here the question:
Given the following structure for document "Restaurant":
{
"_id" : ObjectId("5704adbc2eb7ebe23f582818"),
"address" : {
"building" : "1007",
"coord" : [
-73.856077,
40.848447
],
"street" : "Morris Park Ave",
"zipcode" : "10462"
},
"borough" : "Bronx",
"cuisine" : "Bakery",
"grades" : [
{
"date" : ISODate("2014-03-03T00:00:00Z"),
"grade" : "A",
"score" : 2
},
{
"date" : ISODate("2013-09-11T00:00:00Z"),
"grade" : "A",
"score" : 6
},
{
"date" : ISODate("2013-01-24T00:00:00Z"),
"grade" : "A",
"score" : 10
},
{
"date" : ISODate("2011-11-23T00:00:00Z"),
"grade" : "A",
"score" : 9
},
{
"date" : ISODate("2011-03-10T00:00:00Z"),
"grade" : "B",
"score" : 14
}
],
"name" : "Morris Park Bake Shop",
"restaurant_id" : "30075445"
}
Write a MongoDB query to find the restaurant Id, name and grades for those restaurants where 2nd element of grades array contains a grade of "A" and score 9 on an ISODate "2014-08-11T00:00:00Z".
I wrote this query:
db.restaurants.find(
{
'grades.1': {
'score': 'A',
'grade': 9,
'date' : ISODate("2014-08-11T00:00:00Z")
}
},
{
restaurant_id: 1,
name: 1,
grades: 1
});
which is not working.
The solution provided is the following:
db.restaurants.find(
{ "grades.1.date": ISODate("2014-08-11T00:00:00Z"),
"grades.1.grade":"A" ,
"grades.1.score" : 9
},
{"restaurant_id" : 1,"name":1,"grades":1}
);
My questions are:
is there a way to write the query avoiding to repeat the grades.1 part?
Why is my query wrong, given that grades.1 is a document object?
If it can help answering my question, I am using MongoDB shell version: 3.2.4
EDIT:
I found an answer to question 2 thanks to this question.
In particular I discovered that order matters. Indeed, if I perform the following query, I get a valid result:
db.restaurants.find({'grades.1': {'date': ISODate("2014-08-11T00:00:00Z"), 'grade':'A', score:9}}, {restaurant_id:1, name:1, grades:1})
Note that this query works only because all subdocument's "fields" are specified, and they are specified in the same order.

Not really. But perhaps an explanation of what you "can" do:
db.junk.find({
"grades": {
"$elemMatch": {
"date" : ISODate("2014-03-03T00:00:00Z"),
"grade" : "A",
"score" : 2
}
},
"$where": function() {
var grade = this.grades[0];
return (
grade.date.valueOf() == ISODate("2014-03-03T00:00:00Z").valueOf() &&
grade.grade === "A" &&
grade.score ==== 2
)
}
})
The $elemMatch allows you to shorten a little, but it is not the "nth" element of the array. In order to narrow that further you need to use the $where clause to inspect the "nth" array element to see if all values are a match.
db.junk.aggregate([
{ "$match": {
"grades": {
"$elemMatch": {
"date" : ISODate("2014-03-03T00:00:00Z"),
"grade" : "A",
"score" : 2
}
}
}},
{ "$redact": {
"$cond": {
"if": {
"$let": {
"vars": { "grade": { "$arrayElemAt": [ "$grades", 0 ] } },
"in": {
"$and": [
{ "$eq": [ "$grade.date", ISODate("2014-03-03T00:00:00Z") ] },
{ "$eq": [ "$grade.grade", "A" ] },
{ "$eq": [ "$grade.score", 2 ] }
]
}
}
},
"then": "$$KEEP",
"else": "$$PRUNE"
}
}}
])
You can do the same logic with $redact as well using .aggregate(). It runs a little quicker, but the basic truth should be clear by now.
So using "dot notation" to specify the "nth" position for each element within the array like you have already done is the most efficient and "brief" way to write this. You cannot make it shorter or better.
Your other attempt is looking for a "document" within "grades.1" that matches exactly the document condition you are providing. If for any reason those are not the only fields present, or if they are indeed in "different order" in the stored document, then such a query condition will not be a match.

java.lang.ClassCastException calling RedQueryBuilderFactory.create with args

This line in my JS file:
RedQueryBuilderFactory.create(config,
'SELECT "x0"."title", "x0"."priority" FROM "ticket" "x0" WHERE ("x0"."status" = (?))',
[]
);
works fine witih an empty array as the 3rd parameter. This parameter is supposed to be an array of strings according to the documentation and any sample code I can find. When I pass a string in the array it fails:
RedQueryBuilderFactory.create(config,
'SELECT "x0"."title", "x0"."priority" FROM "ticket" "x0" WHERE ("x0"."status" = (?))',
['in_process']
);
I get java.lang.ClassCastException in the Safari console. Here's the related part of the config if it's relevant:
var config = {
meta : {
tables : [ {
"name" : "ticket",
"label" : "Ticket",
"columns" : [ {
"name" : "title",
"label" : "Title",
"type" : "STRING",
"size" : 255
}, {
"name" : "priority",
"label" : "Priority",
"type" : "REF"
} ],
fks : []
} ],
types : [ {
"name" : "REF",
"editor" : "SELECT",
"operators" : [ {
"name" : "IN",
"label" : "any of",
"cardinality" : "MULTI"
}]
} ]
}
};

Looks like this is a bug in passing in parameter values. Internally it is expecting a collection but this is not happening.
Best if you raise a https://github.com/salk31/RedQueryBuilder bug report here?
NB Should be "IN" not "="