Assuming an api returns response that has products obj such as:
response.products = [{
id: 1,
'productType': 'premium',
}, {
id: 2,
'productType': 'premium',
}, {
id: 3,
'productType': 'free',
}];
let filteredProducts = response.products.filter(p => p.productType === "premium");
response.products = filteredProducts
Does reassigning filteredProducts to response.products creates memory leak? If yes, should I always delete response.product before reassigning new object to it?
let filteredProducts = response.products.filter(p => p.productType === "premium");
delete response.product; //do I need to delete old object so it doesn't become infant(no reference) in memory?
response.products = newProducts
Related
I have a field of type map that contains Maps of data in firestore.
I am trying to retrieve this data using a cloud function in node.js. I can get the document and the data from the field but i can't get it in a usable way. I have tried every solution i can find on SO and google but the below is the only code that can give me access to the data. I obviously need to be able to access each field with in the Map individually. in swift i build an array of String:Any but i can get that to work in Node.JS
const docRef = dbConst.collection('Comps').doc('XEVDk6e4AXZPkNprQRn5Imfcsah11598092006.724980');
return docRef.get().then(docSnap => {
const tagets = docSnap.get('targets')
console.log(tagets);
}).catch(result => { console.log(result) });
this is what i am getting back in the console.
In Swift i do the following and am so far not able to find an equivalent in typescript. (i don't need to build the custom object just ability to access the keys and values)
let obj1 = doc.get("targets") as! [String:Any]
for objs in obj1{
let obs = objs.value as! [String:Any]
let targObj = compUserDetails(IDString: objs.key, activTarg: obs["ActivTarget"] as! Double, stepTarg: obs["StepTarget"] as! Double, name: obs["FullName"] as! String)
UPDATE
After spending a whole day working on it thought i had a solution using the below:
const docRef = dbConst.collection('Comps').doc('XEVDk6e4AXZPkNprQRn5Imfcsah11598092006.724980');
return docRef.get().then(docSnap => {
const tagets = docSnap.get('targets') as [[string, any]];
const newDataMap = [];
for (let [key, value] of Object.entries(tagets)) {
const tempMap = new Map<String,any>();
console.log(key);
const newreWorked = value;
tempMap.set('uid',key);
for(let [key1, value1] of Object.entries(newreWorked)){
tempMap.set(key1,value1);
newDatMap.push(tempMap);
};
};
newDatMap.forEach(element => {
const name = element.get('FullName');
console.log(name);
});
However the new data map has 6 seperate mapped objects. 3 of each of the original objects from the cloud. i can now iterate through and get the data for a given key but i have 3 times as many objects.
So after two days of searching an getting very close i finnaly worked out a solution, it is very similar to the code above but this works. it may not be the "correct" way but it works. feel free to make other suggestions.
return docRef.get().then(docSnap => {
const tagets = docSnap.get('targets') as [[string, any]];
const newDatarray = [];
for (let [key, value] of Object.entries(tagets)) {
const tempMap = new Map<String,any>();
const newreWorked = value;
tempMap.set('uid',key);
for(let [key1, value1] of Object.entries(newreWorked)){
tempMap.set(key1,value1);
};
newDatarray.push(tempMap);
};
newDatarray.forEach(element => {
const name = element.get('FullName');
const steps = element.get('StepTarget');
const avtiv = element.get('ActivTarget');
const UID = element.get('uid');
console.log(name);
console.log(steps);
console.log(avtiv);
console.log(UID);
});
}).catch(result => { console.log(result) });
I made this into a little function that gets the underlying object from a map:
function getMappedValues(map) {
var tempMap = {};
for (const [key, value] of Object.entries(map)) {
tempMap[key] = value;
}
return tempMap;
}
For an object with an array of maps in firestore, you can get the value of the first of those maps like so:
let doc = { // Example firestore document data
items: {
0: {
id: "1",
sr: "A",
},
1: {
id: "2",
sr: "B",
},
2: {
id: "3",
sr: "B",
},
},
};
console.log(getMappedValues(doc.items[0]));
which would read { id: '1', sr: 'A' }
Desired Behaviour
Pull a range of objects from an array of objects and push them back to the array at a new index.
For example, pull objects from the array where their index is between 0 and 2, and push them back to the array at position 6.
For reference, in jQuery, the desired behaviour can be achieved with:
if (before_or_after === "before") {
$("li").eq(new_position).before($("li").slice(range_start, range_end + 1));
} else if (before_or_after === "after") {
$("li").eq(new_position).after($("li").slice(range_start, range_end + 1));
}
jsFiddle demonstration
Schema
{
"_id": ObjectId("*********"),
"title": "title text",
"description": "description text",
"statements": [
{
"text": "string",
"id": "********"
},
{
"text": "string",
"id": "********"
},
{
"text": "string",
"id": "********"
},
{
"text": "string",
"id": "********"
},
{
"text": "string",
"id": "********"
}]
}
What I've Tried
I am able to reposition a single object in an array of objects with the code below.
It uses pull to remove the object from the array and push to add it back to the array at a new position.
In order to do the same for a range of objects, I think I just need to modify the $pull and $push variables but:
I can't figure out how to use $slice in this context, either as a projection or an aggregation, in a $pull operation
Because I can't figure out the first bit, I don't know how to attempt the second bit - the $push operation
// define the topic_id to search for
var topic_id = request_body.topic_id;
// make it usable as a search query
var o_id = new ObjectID(topic_id);
// define the statement_id to search for
var statement_id = request_body.statement_id;
// define new position
var new_position = Number(request_body.new_position);
// define old position
var old_position = Number(request_body.old_position);
// define before or after (this will be relevant later)
// var before_or_after = request_body.before_or_after;
// define the filter
var filter = { _id: o_id };
// define the pull update - to remove the object from the array of objects
var pull_update = {
$pull: {
statements: { id: statement_id } // <----- how do i pull a range of objects here
}
};
// define the projection so that only the 'statements' array is returned
var options = { projection: { statements: 1 } };
try {
// perform the pull update
var topic = await collection.findOneAndUpdate(filter, pull_update, options);
// get the returned statement object so that it can be inserted at the desired index
var returned_statement = topic.value.statements[old_position];
// define the push update - to add the object back to the array at the desired position
var push_update = {
$push: {
statements: {
$each: [returned_statement],
$position: new_position
}
} // <----- how do i push the range of objects back into the array here
};
// perform the push update
var topic = await collection.findOneAndUpdate(filter, push_update);
}
Environments
##### local
$ mongod --version
db version v4.0.3
$ npm view mongodb version
3.5.9
$ node -v
v10.16.3
$ systeminfo
OS Name: Microsoft Windows 10 Home
OS Version: 10.0.18363 N/A Build 18363
##### production
$ mongod --version
db version v3.6.3
$ npm view mongodb version
3.5.9
$ node -v
v8.11.4
RedHat OpenShift Online, Linux
Edit
Gradually, figuring out parts of the problem, I think:
Using the example here, the following returns objects from array with index 0 - 2 (ie 3 objects):
db.topics.aggregate([
{ "$match": { "_id": ObjectId("********") } },
{ "$project": { "statements": { "$slice": ["$statements", 0, 3] }, _id: 0 } }
])
Not sure how to use that in a pull yet...
I also looked into using $in (even though i would prefer to just grab a range of objects than have to specify each object's id), but realised it does not preserve the order of the array values provided in the results returned:
Does MongoDB's $in clause guarantee order
Here is one solution to re-ordering results from $in in Node:
https://stackoverflow.com/a/34751295
Here an example with mongo 3.5
const mongo = require('mongodb')
;(async function (params) {
const client = await mongo.connect('mongodb://localhost:27017')
const coll = client.db('test').collection('test')
const from0to99 = Array(100).fill('0').map((_, i) => String(i))
const from5To28 = Array(24).fill('0').map((_, i) => String(i + 5))
const insert = { statements: from0to99.map(_ => ({ id: _ })) }
await coll.insertOne(insert)
const all100ElementsRead = await coll.findOneAndUpdate(
{ _id: insert._id },
{
$pull: {
statements: {
id: { $in: from5To28 }
}
}
},
{ returnOriginal: true }
)
/**
* It shows the object with the desired _id BEFORE doing the $pull
* You can process all the old elements as you wish
*/
console.log(all100ElementsRead.value.statements)
// I use the object read from the database to push back
// since I know the $in condition, I must filter the array returned
const pushBack = all100ElementsRead.value.statements.filter(_ => from5To28.includes(_.id))
// push back the 5-28 range at position 72
const pushed = await coll.findOneAndUpdate(
{ _id: insert._id },
{
$push: {
statements: {
$each: pushBack,
$position: 72 // 0-indexed
}
}
},
{ returnOriginal: false }
)
console.log(pushed.value.statements) // show all the 100 elements
client.close()
})()
This old issue helped
if you want "desired behavior" when mutating arrays ,
you add these to checklist:
array.length atleast==7 if you want to add ,splice at 6
creates a new array if u use concat
mutates orignal if used array.push or splice or a[a.length]='apple'
USE slice() to select between incex1 to index2.
or run a native for loop to select few elements of array or
apply a array.filter() finction.
once you select your elements which needed to be manupulated you mentioned you want to add it to end. so this is the method below.
about adding elements at end:
CONCAT EXAMPLE
const original = ['🦊']; //const does not mean its immutable just that it cant be reassigned
let newArray;
newArray = original.concat('🦄');
newArray = [...original, '🦄'];
// Result
newArray; // ['🦊', '🦄']
original; // ['🦊']
SPLICE EXAMPLE:
const zoo = ['🦊', '🐮'];
zoo.splice(
zoo.length, // We want add at the END of our array
0, // We do NOT want to remove any item
'🐧', '🐦', '🐤', // These are the items we want to add
);
console.log(zoo); // ['🦊', '🐮', '🐧', '🐦', '🐤']
I am trying to develop a discord bot with nodejs. My question is how do I get a specific data out of a JSON file (for instance, from this json. I want to only specify a single uuid like "59d4c622c7cc459a98c2e947054e2b11" and get the data.
Assuming you have already parsed the JSON into an actual Javascript object named data and given the way the data is currently organized, you would have to search the data.guild.members array to find the object that had the desired uuid property value.
function findDataForUuid(uuid) {
for (let obj of data.guild.members) {
if (obj.uuid === uuid) {
return obj;
}
}
// no match found
return null;
}
let item = findDataForUuid("59d4c622c7cc459a98c2e947054e2b11");
if (item) {
console.log(item); // will show all the properties of the member object
}
Or, using .find() on the array:
function findDataForUuid(uuid) {
return data.guild.members.find(item => {
return item.uuid === uuid;
});
}
The simple soln you can use filter. Best is use reduce.
const data = {
guild: {
_id: "5b2906070cf29ddccd0f203c",
name: "Dulcet",
coins: 122010,
coinsEver: 232010,
created: 1529415175560,
members: [
{
uuid: "59d4c622c7cc459a98c2e947054e2b11",
rank: "MEMBER",
joined: 1529683128302,
questParticipation: 39,
expHistory: {
"2020-02-16": 0,
"2020-02-15": 0,
"2020-02-14": 0,
"2020-02-13": 0,
"2020-02-12": 0,
"2020-02-11": 0,
"2020-02-10": 0
}
}
]
}
};
const members = data.guild.members.filter(
member => member.uuid == "59d4c622c7cc459a98c2e947054e2b11"
);
const firstMember = members[0]
console.log(firstMember)
I try to split a sub-object in my recordset when importing data with initCB properties of a Column in ColumnSet.
But when I use two different init functions for two different destination names but one source I get same result.
const cs = new pgp.helpers.ColumnSet([
'id',
{ name: 'source_id', prop: 'source', init: function(obj) { return obj.value.id; } },
{ name: 'source_name', prop: 'source', init: function(obj) { return obj.value.name; } },
], { table: 'test_table' });
const data = [
{ id: 1, source: { id: 1, name: 'source1' } },
{ id: 2, source: { id: 1, name: 'source1' } },
{ id: 3, source: { id: 2, name: 'source2' } },
];
const insert = pgp.helpers.insert(data, cs);
The result is:
INSERT INTO "test_table"("id","source_id","source_name") VALUES
(1,'source1','source1'),
(2,'source1','source1'),
(3,'source2','source2')
instead of expected:
INSERT INTO "test_table"("id","source_id","source_name") VALUES
(1,1,'source1'),
(2,1,'source1'),
(3,2,'source2')
It seems like second invocation of callback function for THE SAME source field overriding result of previous invocation of ANOTHER callback function on THIS source field.
How I can avoid this?
Or there is another way of splitting a sub-object during import?
Option prop doesn't quite work that way. It is there to remap the value to a different property name, but it does not supply the direct object reference.
Instead, use property source of the column descriptor, to reference the source object. Ironically, you called the property in your data source as well, which means you will have to use source twice in your reference:
const cs = new pgp.helpers.ColumnSet([
'id',
{name: 'source_id', init: c => c.source.source.id},
{name: 'source_name', init: c => c.source.source.name}
], {table: 'test_table'});
The first source is what pg-promise API supports, while the second is your data column name :)
Also, as per documentation, the API sets source and this to the same, so if you prefer the ES5 function syntax (looks cleaner for your example), then you can do this instead:
const cs = new pgp.helpers.ColumnSet([
'id',
{ name: 'source_id', init: function() {return this.source.id;}},
{ name: 'source_name', init: function() {return this.source.name;}},
], { table: 'test_table' });
Above we have this point at the source data object.
in our application we used to query data with coll.find() method and it returned Cursor instance from which I could retrieve all the data needed for the client.
const coll: Collection = await this.ensureCollection(collection);
let query = { ... };
let result: Cursor = await coll.find(query);
let total: Cursor = await coll.count(query);
let readResult = {
offset: result.cursorState.skip,
limit: result.cursorState.currentLimit,
total,
data: result.toArray();
}
I'm trying to move it to aggregation for our new filter system.
const coll: Collection = await this.ensureCollection(collection);
let query = [{ $skip: ... }, { $limit: ... }];
let result = await coll.aggregate(query);
let limit: number;
let offset: number;
let limitPipeline: any = aggregationQuery.find(pipeline => (typeof pipeline.$limit !== 'undefined'));
if (limitPipeline) {
limit = limitPipeline.$limit;
}
let offsetPipeline: any = aggregationQuery.find(pipeline => (typeof pipeline.$skip !== 'undefined'));
if (offsetPipeline) {
offset = offsetPipeline.$skip;
}
let total: number = ???
let readResult = {
offset,
limit,
total,
data: result.toArray();
}
Questions:
1) How do I get limit and offset properly? The way I get limit and offset isn't safe. The way I retrieved them when I was using coll.find() method doesn't not work with aggregation.
2) How do I get total amount of documents my query returns?
I'd like to know how it's done in real applications, best practices.
Thanks.