Related
Given the following sample JSON (stringified from the corresponding JavaScript object), I need to extract this information:
Find the object in persons which has the reference = 2.
If a person with this reference was found, get the name of the person's parent element (here: "B").
In the end, I need to build a new object looking similar to this. This won't be problematic but I'm struggling with how to extract these objects from the source. I tried different approaches with find(), map(), flatMap() and filter() but none of them really worked.
{
companyName: "B",
person: {
"reference": 2,
"name": "Bob"
}
}
Source
{
"root": [
{
"companies": [
{
"name": "A",
"persons": [
{
"reference": 1,
"name": "Alex"
}
]
}
]
},
{
"companies": [
{
"name": "B",
"persons": [
{
"reference": 2,
"name": "Bob"
},
{
"reference": 3,
"name": "Charles"
}
]
}
]
}
]
}
If you're just interested in the name of the company you can find it using:
const reference = 2;
const company = data.root.flatMap(item => item.companies)
.find(company => company.persons.some(person => person.reference === reference));
const companyName = company?.name;
// or if you cannot use optional chaining
const companyName = (company || {}).name;
In data.root.flatMap(item => item.companies) we iterate through all items in root, for each item we select its companies property. Since we don't want a nested array we use flatMap() to flatten the result by 1 level. This leaves us with an array of companies.
After that we'll call find() on the companies array, since we are looking for a specific company name. The criteria of the company is that some() (1 or more) of the persons should match the provided reference. If no match is found null will be returned (from find()).
We then take the find() result (company) and navigate to the name via optional chaining ?.. This will return the name of the company if present, or undefined if company is null
You can use array.reduce here
let data = JSON.parse(`{
"root": [
{
"companies": [
{
"name": "A",
"persons": [
{
"reference": 1,
"name": "Alex"
}
]
}
]
},
{
"companies": [
{
"name": "B",
"persons": [
{
"reference": 2,
"name": "Bob"
},
{
"reference": 3,
"name": "Charles"
}
]
}
]
}
]
}`)
// GET ALL THE COMPANIES DATA
let companies = data.root.reduce(
(prevValue, currValue) => {
prevValue.push(...currValue.companies)
return prevValue
},
[]
)
// FIND AND CREATE EXPECTED RESULT SET
let results = companies.reduce(
(prevValue, currValue) => {
// loop inside a loop, mind it
let refPerson = currValue.persons.find((item)=> item.reference == 2)
if(refPerson){
prevValue.push({
companyName: currValue.name,
person: refPerson
})
}
return prevValue
},
[]
)
console.log(results)
This question already has answers here:
Find all values by specific key in a deep nested object
(11 answers)
Closed 10 months ago.
I have this JSON array tree that can include any number of nested arrays:
const namesArrayTree = [
{
"name": "Peter"
},
{
"name": "folder1",
"isArray": true,
"namesArray": [
{
"name": "Paul"
},
{
"name": "folder2",
"isArray": true,
"namesArray": [
{
"name": "Mary"
},
{
"name": "John"
}
]
}
]
},
{
"name": "Mark"
}
]
I need to transform it to a flat array including only the names:
const namesArrayFlat = [ "Peter", "Paul", "Mary", "John", "Mark" ]
So I'm using this code to do the transformation:
const namesArrayTree = [
{
"name": "Peter"
},
{
"name": "folder1",
"isArray": true,
"namesArray": [
{
"name": "Paul"
},
{
"name": "folder2",
"isArray": true,
"namesArray": [
{
"name": "Mary"
},
{
"name": "John"
}
]
}
]
},
{
"name": "Mark"
}
] ;
function getNamesList(item) {
let name = item.name;
let isArray = item.isArray;
if (isArray) {
name = item.namesArray.map(getNamesList).join("\r\n");
}
return name;
}
const namesList = namesArrayTree.map(getNamesList).join("\r\n");
const namesArrayFlat = namesList.split("\r\n");
console.log(namesArrayFlat)
The code works well, but I would like to get rid of the extra steps to create a list with the names using join.("\r\n") and then convert to array using split("\r\n").
That is, I would like to reduce the code by removing the following:
function getNamesList(item) {
let name = item.name;
let isArray = item.isArray;
if (isArray) {
/* remove code to join by "\r\n" */
name = item.namesArray.map(getNamesList)
}
return name;
}
/* remove code to create "namesList" constant and remove code to join by "\r\n") */
const namesArrayFlat = namesArrayTree.map(getNamesList)
console.log(namesArrayFlat)
(The above code still returns a tree nested arrays structure)
Any ideas about how to get rid of the extra code? also any suggestions about how to improve the code would be great, thanks!
function getNamesList(item) {
return item.isArray ? item.namesArray.map(getNamesList) : item.name
}
const names = namesArrayTree.map(getNamesList).flat(Infinity)
console.log(names)
You can achieve this with an array reducer as follows:
const namesArray = [
{
"name": "Peter"
},
{
"name": "folder1",
"isArray": true,
"namesArray": [
{
"name": "Paul"
},
{
"name": "folder2",
"isArray": true,
"namesArray": [
{
"name": "Mary"
},
{
"name": "John"
}
]
}
]
},
{
"name": "Mark"
}
] ;
function reduceNamesList(list, item) {
if (item.isArray) {
return item.namesArray.reduce(reduceNamesList, list);
}
list.push(item.name)
return list
}
const namesList = namesArray.reduce(reduceNamesList, [])
console.log(namesList)
I have a multilevel nested document (its dynamic and some levels can be missing but maximum 3 levels). I want to update all the children and subchildren routes if any. The scenario is same as in any Windows explorer, where all subfolders' route need to change when a parent folder route is changed. For eg. In the below example, If I am at route=="l1/l2a" and it's name needs to be edited to "l2c", then I will update it's route as route="l1/l2c and I will update all childrens' route to say "l1/l2c/l3a".
{
"name":"l1",
"route": "l1",
"children":
[
{
"name": "l2a",
"route": "l1/l2a",
"children":
[
{
"name": "l3a",
"route": "l1/l2a/l3a"
}]
},
{
"name": "l2b",
"route": "l1/l2b",
"children":
[
{
"name": "l3b",
"route": "l1/l2b/l3b"
}]
}
]
}
Currently I am able to go to a point and I am able to change its name and ONLY its route in the following manner:
router.put('/navlist',(req,res,next)=>{
newname=req.body.newName //suppose l2c
oldname=req.body.name //suppose l2a
route=req.body.route // existing route is l1/l2a
id=req.body._id
newroute=route.replace(oldname,newname); // l1/l2a has to be changed to l1/l2c
let segments = route.split('/');
let query = { route: segments[0]};
let update, options = {};
let updatePath = "";
options.arrayFilters = [];
for(let i = 0; i < segments.length -1; i++){
updatePath += `children.$[child${i}].`;
options.arrayFilters.push({ [`child${i}.route`]: segments.slice(0, i + 2).join('/') });
} //this is basically for the nested children
updateName=updatePath+'name'
updateRoute=updatePath+'route';
update = { $setOnInsert: { [updateName]:newDisplayName,[updateRoute]:newroute } };
NavItems.updateOne(query,update, options)
})
The problem is I am not able to edit the routes of it's children if any i.e it's subfolder route as l1/l2c/l3a. Although I tried using the $[] operator as follows.
updateChild = updatePath+'.children.$[].route'
updateChild2 = updatePath+'.children.$[].children.$[].route'
//update = { $set: { [updateChild]:'abc',[updateChild2]:'abc' } };
Its important that levels are customizable and thus I don't know whether there is "l3A" or not. Like there can be "l3A" but there may not be "l3B". But my code simply requires every correct path else it gives an error
code 500 MongoError: The path 'children.1.children' must exist in the document in order to apply array updates.
So the question is how can I apply changes using $set to a path that actually exists and how can I edit the existing route part. If the path exists, it's well and good and if the path does not exist, I am getting the ERROR.
Update
You could simplify updates when you use references.Updates/Inserts are straightforward as you can only the update target level or insert new level without worrying about updating all levels. Let the aggregation takes care of populating all levels and generating route field.
Working example - https://mongoplayground.net/p/TKMsvpkbBMn
Structure
[
{
"_id": 1,
"name": "l1",
"children": [
2,
3
]
},
{
"_id": 2,
"name": "l2a",
"children": [
4
]
},
{
"_id": 3,
"name": "l2b",
"children": [
5
]
},
{
"_id": 4,
"name": "l3a",
"children": []
},
{
"_id": 5,
"name": "l3b",
"children": []
}
]
Insert query
db.collection.insert({"_id": 4, "name": "l3a", "children": []}); // Inserting empty array simplifies aggregation query
Update query
db.collection.update({"_id": 4}, {"$set": "name": "l3c"});
Aggregation
db.collection.aggregate([
{"$match":{"_id":1}},
{"$lookup":{
"from":"collection",
"let":{"name":"$name","children":"$children"},
"pipeline":[
{"$match":{"$expr":{"$in":["$_id","$$children"]}}},
{"$addFields":{"route":{"$concat":["$$name","/","$name"]}}},
{"$lookup":{
"from":"collection",
"let":{"route":"$route","children":"$children"},
"pipeline":[
{"$match":{"$expr":{"$in":["$_id","$$children"]}}},
{"$addFields":{"route":{"$concat":["$$route","/","$name"]}}}
],
"as":"children"
}}
],
"as":"children"
}}
])
Original
You could make route as array type and format before presenting it to user. It will greatly simplify updates for you. You have to break queries into multiple updates when nested levels don’t exist ( ex level 2 update ). May be use transactions to perform multiple updates in atomic way.
Something like
[
{
"_id": 1,
"name": "l1",
"route": "l1",
"children": [
{
"name": "l2a",
"route": [
"l1",
"l2a"
],
"children": [
{
"name": "l3a",
"route": [
"l1",
"l2a",
"l3a"
]
}
]
}
]
}
]
level 1 update
db.collection.update({
"_id": 1
},
{
"$set": {
"name": "m1",
"route": "m1"
},
"$set": {
"children.$[].route.0": "m1",
"children.$[].children.$[].route.0": "m1"
}
})
level 2 update
db.collection.update({
"_id": 1
},
{
"$set": {
"children.$[child].route.1": "m2a",
"children.$[child].name": "m2a"
}
},
{
"arrayFilters":[{"child.name": "l2a" }]
})
db.collection.update({
"_id": 1
},
{
"$set": {
"children.$[child].children.$[].route.1": "m2a"
}
},
{
"arrayFilters":[{"child.name": "l2a"}]
})
level 3 update
db.collection.update({
"_id": 1
},
{
"$set": {
"children.$[].children.$[child].name": "m3a"
"children.$[].children.$[child].route.2": "m3a"
}
},
{
"arrayFilters":[{"child.name": "l3a"}]
})
I don't think its possible with arrayFilted for first level and second level update, but yes its possible only for third level update,
The possible way is you can use update with aggregation pipeline starting from MongoDB 4.2,
I am just suggesting a method, you can simplify more on this and reduce query as per your understanding!
Use $map to iterate the loop of children array and check condition using $cond, and merge objects using $mergeObjects,
let id = req.body._id;
let oldname = req.body.name;
let route = req.body.route;
let newname = req.body.newName;
let segments = route.split('/');
LEVEL 1 UPDATE: Playground
// LEVEL 1: Example Values in variables
// let oldname = "l1";
// let route = "l1";
// let newname = "l4";
if(segments.length === 1) {
let result = await NavItems.updateOne(
{ _id: id },
[{
$set: {
name: newname,
route: newname,
children: {
$map: {
input: "$children",
as: "a2",
in: {
$mergeObjects: [
"$$a2",
{
route: { $concat: [newname, "/", "$$a2.name"] },
children: {
$map: {
input: "$$a2.children",
as: "a3",
in: {
$mergeObjects: [
"$$a3",
{ route: { $concat: [newname, "/", "$$a2.name", "/", "$$a3.name"] } }
]
}
}
}
}
]
}
}
}
}
}]
);
}
LEVEL 2 UPDATE: Playground
// LEVEL 2: Example Values in variables
// let oldname = "l2a";
// let route = "l1/l2a";
// let newname = "l2g";
else if (segments.length === 2) {
let result = await NavItems.updateOne(
{ _id: id },
[{
$set: {
children: {
$map: {
input: "$children",
as: "a2",
in: {
$mergeObjects: [
"$$a2",
{
$cond: [
{ $eq: ["$$a2.name", oldname] },
{
name: newname,
route: { $concat: ["$name", "/", newname] },
children: {
$map: {
input: "$$a2.children",
as: "a3",
in: {
$mergeObjects: [
"$$a3",
{ route: { $concat: ["$name", "/", newname, "/", "$$a3.name"] } }
]
}
}
}
},
{}
]
}
]
}
}
}
}
}]
);
}
LEVEL 3 UPDATE: Playground
// LEVEL 3 Example Values in variables
// let oldname = "l3a";
// let route = "l1/l2a/l3a";
// let newname = "l3g";
else if (segments.length === 3) {
let result = await NavItems.updateOne(
{ _id: id },
[{
$set: {
children: {
$map: {
input: "$children",
as: "a2",
in: {
$mergeObjects: [
"$$a2",
{
$cond: [
{ $eq: ["$$a2.name", segments[1]] },
{
children: {
$map: {
input: "$$a2.children",
as: "a3",
in: {
$mergeObjects: [
"$$a3",
{
$cond: [
{ $eq: ["$$a3.name", oldname] },
{
name: newname,
route: { $concat: ["$name", "/", "$$a2.name", "/", newname] }
},
{}
]
}
]
}
}
}
},
{}
]
}
]
}
}
}
}
}]
);
}
Why separate query for each level?
You could do single query but it will update all level's data whenever you just need to update single level data or particular level's data, I know this is lengthy code and queries but i can say this is optimized version for query operation.
you can't do as you want. Because mongo does not support it. I can offer you to fetch needed item from mongo. Update him with your custom recursive function help. And do db.collection.updateOne(_id, { $set: data })
function updateRouteRecursive(item) {
// case when need to stop our recursive function
if (!item.children) {
// do update item route and return modified item
return item;
}
// case what happen when we have children on each children array
}
I have this nested object (json):
const json = {
"application": {
"App1": {
"cats": [
1
]
},
"App2": {
"cats": [
3
]
},
"App3": {
"cats": [
1,
2
]
}
},
"categories": {
"1": {
"name": "FirstCategory"
},
"2": {
"name": "SecondCategory"
},
"3": {
"name": "ThirdCategory"
}
}
};
This object has two main properties: application and categories.
I want to map over application's cats array and get name property of each element of cats array.
So the final result should look like:
{
"App1": "FirstCategory",
"App2": "ThirdCategory",
"App3": "FirstCategory, ThirdCategory"
}
I have tried to use map function, but the main difficulty is that inside applicaiton property cats is array (can have multiple values). So the code below didn't work:
Object.values(json.application).map(val => {
Object.keys(json.categories).map(key => {
//print something
});
});
You can use Array.reduce for an elegant solution.
const json = {
"application": {
"App1": {
"cats": [
1
]
},
"App2": {
"cats": [
3
]
},
"App3": {
"cats": [
1,
2
]
}
},
"categories": {
"1": {
"name": "FirstCategory"
},
"2": {
"name": "SecondCategory"
},
"3": {
"name": "ThirdCategory"
}
}
};
//Getting Application object
const application = json.application
//Getting Categories object
const categories = json.categories
//initializing reduce with a blank object and pushing all the keys of the application object
//Looping over keys of application object
const requiredOutput = Object.keys(application).reduce((out, appKey) => {
//Setting value based on categories name
out[appKey] = application[appKey].cats.map(id => categories[id].name)
return out
}, {})
console.log(requiredOutput)
PS: You can refer this gist for safe reading from a nested object.
Try it with this.
for(let val in json.application){
json.application[val] = json.application[val].cats.map(cat => json.categories[cat].name).join(",")
}
const result = Object.keys(json.application).reduce((a,key) => {
a[key] = json.application[key].cats
.map(cat => json.categories[cat].name)
.join(", ")
return a;
}, {})
loop over keys of application
for each key loop over car, and for each cat return string value from category
join list of cat strings
So I have a bunch of status codes, in an object (from an API) that returns like this:
{
"location": [
"HOME_ADDRESS_INCOMPLETE",
"HOME_MISSING_ADDRESS"
],
"basics": [
"HOME_MISSING_TYPE"
],
"description": [
"HOME_MISSING_DESCRIPTION"
],
"immersions": [
"AT_LEAST_ONE_STAY_REQUIRED",
"SIMPLE_STAY_MISSING_HOURS",
"SIMPLE_STAY_MISSING_OFFERED_LANGUAGES",
"TANDEM_STAY_MISSING_HOURS",
"TANDEM_STAY_MISSING_OFFERED_LANGUAGES",
"TANDEM_STAY_MISSING_INTERESTED_LANGUAGES",
"TEACHER_STAY_MISSING_HOURLY_PRICE",
"TEACHER_STAY_MISSING_OFFERED_LANGUAGES",
"TEACHER_STAY_MISSING_WEEKLY_PACKAGES"
],
"rooms": [
"NO_ROOMS"
],
"photos": [
"AT_LEAST_ONE_HOME_IMAGE_REQUIRED"
],
"pricing": [
"MISSING_CURRENCY",
"SERVICE_WITHOUT_PRICE",
"DISCOUNT_WITHOUT_PERCENT",
"ROOM_WITHOUT_PRICE"
]
}
The key names, like location correlate to a step in a setup wizard that the user must be placed on depending on what is missing, which is represented by constants like HOME_ADDRESS_INCOMPLETE.
What is the most terse or clear way to start with this object and one constant, like MISSING_CURRENCY, and return the name of the key to which that constant's array belongs to?
Here's what I have so far, but all it does is return the array itself:
const activeStep = Object.values(HomeStatusCodes).filter(statusArray => {
return statusArray.includes(homeActivationResponse.code)
})
Array#find (on the array of keys of that structure, from Object.keys) plus Array#indexOf should do it:
function find(value) {
return Object.keys(data).find(function(key) {
return data[key].indexOf(value) != -1;
});
}
Note that Array#find is new in ES2015, but can readily be shimmed/polyfilled.
Example:
var data = {
"location": [
"HOME_ADDRESS_INCOMPLETE",
"HOME_MISSING_ADDRESS"
],
"basics": [
"HOME_MISSING_TYPE"
],
"description": [
"HOME_MISSING_DESCRIPTION"
],
"immersions": [
"AT_LEAST_ONE_STAY_REQUIRED",
"SIMPLE_STAY_MISSING_HOURS",
"SIMPLE_STAY_MISSING_OFFERED_LANGUAGES",
"TANDEM_STAY_MISSING_HOURS",
"TANDEM_STAY_MISSING_OFFERED_LANGUAGES",
"TANDEM_STAY_MISSING_INTERESTED_LANGUAGES",
"TEACHER_STAY_MISSING_HOURLY_PRICE",
"TEACHER_STAY_MISSING_OFFERED_LANGUAGES",
"TEACHER_STAY_MISSING_WEEKLY_PACKAGES"
],
"rooms": [
"NO_ROOMS"
],
"photos": [
"AT_LEAST_ONE_HOME_IMAGE_REQUIRED"
],
"pricing": [
"MISSING_CURRENCY",
"SERVICE_WITHOUT_PRICE",
"DISCOUNT_WITHOUT_PERCENT",
"ROOM_WITHOUT_PRICE"
]
};
function find(value) {
return Object.keys(data).find(function(key) {
return data[key].indexOf(value) != -1;
});
}
console.log(find("MISSING_CURRENCY"));
Even more terse when you use ES2015 syntax:
const find = value =>
Object.keys(data).find(key => data[key].indexOf(value) != -1);
(Yes, that's really a function.) Here's a live version of that for browsers that support ES2015:
var data = {
"location": [
"HOME_ADDRESS_INCOMPLETE",
"HOME_MISSING_ADDRESS"
],
"basics": [
"HOME_MISSING_TYPE"
],
"description": [
"HOME_MISSING_DESCRIPTION"
],
"immersions": [
"AT_LEAST_ONE_STAY_REQUIRED",
"SIMPLE_STAY_MISSING_HOURS",
"SIMPLE_STAY_MISSING_OFFERED_LANGUAGES",
"TANDEM_STAY_MISSING_HOURS",
"TANDEM_STAY_MISSING_OFFERED_LANGUAGES",
"TANDEM_STAY_MISSING_INTERESTED_LANGUAGES",
"TEACHER_STAY_MISSING_HOURLY_PRICE",
"TEACHER_STAY_MISSING_OFFERED_LANGUAGES",
"TEACHER_STAY_MISSING_WEEKLY_PACKAGES"
],
"rooms": [
"NO_ROOMS"
],
"photos": [
"AT_LEAST_ONE_HOME_IMAGE_REQUIRED"
],
"pricing": [
"MISSING_CURRENCY",
"SERVICE_WITHOUT_PRICE",
"DISCOUNT_WITHOUT_PERCENT",
"ROOM_WITHOUT_PRICE"
]
};
const find = value =>
Object.keys(data).find(key => data[key].indexOf(value) != -1);
console.log(find("MISSING_CURRENCY"));
You could iterate the keys and find the one which property includes the wanted item.
function getKey(object, item) {
return Object.keys(object).find(k => object[k].includes(item));
}
var data = { "location": ["HOME_ADDRESS_INCOMPLETE", "HOME_MISSING_ADDRESS"], "basics": ["HOME_MISSING_TYPE"], "description": ["HOME_MISSING_DESCRIPTION"], "immersions": ["AT_LEAST_ONE_STAY_REQUIRED", "SIMPLE_STAY_MISSING_HOURS", "SIMPLE_STAY_MISSING_OFFERED_LANGUAGES", "TANDEM_STAY_MISSING_HOURS", "TANDEM_STAY_MISSING_OFFERED_LANGUAGES", "TANDEM_STAY_MISSING_INTERESTED_LANGUAGES", "TEACHER_STAY_MISSING_HOURLY_PRICE", "TEACHER_STAY_MISSING_OFFERED_LANGUAGES", "TEACHER_STAY_MISSING_WEEKLY_PACKAGES"], "rooms": ["NO_ROOMS"], "photos": ["AT_LEAST_ONE_HOME_IMAGE_REQUIRED"], "pricing": ["MISSING_CURRENCY", "SERVICE_WITHOUT_PRICE", "DISCOUNT_WITHOUT_PERCENT", "ROOM_WITHOUT_PRICE"] };
console.log(getKey(data, 'MISSING_CURRENCY'));
I'd go for a lookup map:
const stepByStatusCode = new Map()
for (const step in HomeStatusCodes) {
for (const code of HomeStatusCodes[step])
stepByStatusCode.set(code, step);
which you then can use in the most terse way
const activeStep = stepByStatusCode.get(homeActivationResponse.code);