Basically I got my app up an running but I'm stuck with a problem: if I pass an object that contains an empty array to be saved, the array is not saved into the db. I'm not sure this is a problem in js or the mongo driver, but in order to save the empty array I need to pass the array like so: products: [''].
This is the structure of my mongo document:
_id: ObjectId(...),
name: 'String',
subcategories: [
{
subcategory: 'string',
products: [
{
name: 'string'
price: integer
}
]
}
]
So in my front-end I'm grabbing the whole document through an ajax call pushing a new object into the subcategories array. The new object looks like this:
{subcategory:'string', products:['']}
And this works okay until I need to insert a new object inside the array: Because I've grabbed the whole object, pushed the new object to the array, the previous one looks like this:
{subcategory: 'string'}
Having lost the mention to products:[] array in the process.
How can I get around this? I need to be able to have empty arrays in my object.
EDIT
What I did on front end: Got the whole object with $.get which returned:
var obj =
_id: ObjectId(...),
name: 'String',
subcategories: [
{
subcategory: 'Subcategory1',
products: [
{
name: 'string'
price: integer
}
]
}
];
Then on the front end I've pushed the new object category inside the subcategories array:
data.subcategories.push({subcategory: 'Subcategory2', products: ['']})
Where subcat was a string with the category name. On my db I could see that I've successfully added the object:
var obj =
_id: ObjectId(...),
name: 'String',
subcategories: [
{
subcategory: 'Subcategory1',
products: [
{
name: 'string'
price: integer
}
]
},
{
subcategory: 'Subcategory2'
products: []
}
];
The problem was when I wanted to add another subcategory, the previous one return empty:
var obj =
_id: ObjectId(...),
name: 'String',
subcategories: [
{
subcategory: 'Subcategory1',
products: [
{
name: 'string'
price: integer
}
]
},
{
subcategory: 'Subcategory2'
},
{
subcategory: 'Subcategory3'
products: []
},
];
Because at some point the empty array was removed from the object. Like I said, I did fix this in the front end, so the error jade was throwing has been addressed, but I still find odd that the products: [] was being removed from the document.
I'm new to MongoDb and node, not to mention that I'm also new with JS, so it might well be a feature that I'm unaware of.
When passing empty arrays to Mongo they are interpreted as empty documents, {}. Zend Json encoder will interpret them as empty arrays []. I understand that it's not possible to tell which one is correct.
Incase of empty arrays try posting as
Array[null];
instead of Array[];
This will be working fine
When passing empty arrays to Mongo they are interpreted as empty documents, {}. Zend Json encoder will interpret them as empty arrays []. I understand that it's not possible to tell which one is correct.
In my view it's more logical that the actual php array (when empty) is interpreted as an array in MongoDB. Although that will require something else to identify empty documents it's still more logical than the current behaviour.
A possible solution would be to introduce a new object, MongoEmptyObject (or using the stdObj) whenever one want to introduce an empty object.
Meanwhile, a workaround is to detect empty arrays in php, and inject a null value $arr[0] = null;
Then the object will be interpreted as an empty array in mongo.
The workaround works both in PHP and in the mongo console. Question: does json allow for arrays with null values? If so, then the workaround is a sign of another bug.
PHP:
if (is_array($value) && empty($value))
{ $value[0] = null; }
Mongo Console:
var b =
{hej:"da", arr: [null]}
db.test.save(b);
db.test.find();
{"_id" : "4a4b23adde08d50628564b12" , "hej" : "da" , "arr" : []}
Related
I'm working on building a database from a set of CSV files and am running into issues pushing elements to a deeply nested array. I've seen examples for 2D arrays and the use of positional operators but I can't quite figure out how to use them for my situation.
What I am trying to do read the CSV file which has columns for the answer_id and the url string for the photo. I want to push the url string to the photos array for the corresponding answer_id. When I try to use the code below, I get a long error message which starts with:
MongoBulkWriteError: Cannot create field 'answers' in element
{
results: [
{
question_id: "1",
_id: ObjectId('6332e0b015c1d1f4eccebf4e'),
answers: [
{
answer_id: "5",
//....
}
],
}
]
}
I formatted the above message to make things easier to read. It may be worth noting the first row of my CSV file has '5' in the answer_id column which makes me think things are failing at the first try to update my document.
Here is an example of my code:
const ExampleModel = new Schema({
example_id: String,
results: [
{
question_id: String,
answers: [
{
answer_id: String,
photos: [
{ url: String },
]
}
]
}
]
});
// Example Operation
// row.answer_id comes from CSV file
updateOne: {
'filter': {
'results.answers.answer_id': row.answer_id,
},
'update': {
'$push': {
'results.answers.$.photos' : { 'url': 'test'}
}
}
}
I guess my question is can I update an array this deeply nested using Mongoose?
I am receiving a json response from an API call. I need to store its keys, and create an array of an object. I am intending to this array of an object is created dynamically no matter the keys of the response.
I've already got the keys like this:
const json_getAllKeys = data => {
const keys = data.reduce((keys, obj) => (
keys.concat(Object.keys(obj).filter(key => (
keys.indexOf(key) === -1))
)
), [])
return keys
}
That returned an array (using a sample json):
['name','username', 'email']
But I am trying to use that array to create an array of object that looks like this one
[
{
name: "name",
username: "username",
email: "Email",
}
];
I've been trying mapping the array, but got multiple objects because of the loop, and I need a single one to make it work.
keys.map(i=>({i:i}))
[
{ i: 'id' },
{ i: 'name' },
{ i: 'username' },
{ i: 'email' }
]
Any hint would be useful!
Thanks in advance :D
What you're looking for is Object.fromEntries, which is ECMA2019, I believe, so available in Node >=14 and will be provided as a polyfill if you employ babel.
I can't quite discern what your reduce should produce, but given the sample input, I would write
const input = ['name','username', 'email'];
const result = Object.fromEntries(input.map(name => ([name, name])));
// result == { name: 'name', username: 'username', email: 'email' }
You're definitely on the right track. One thing to remember is the map function will return the SAME number of output as input. So in your example, an array of 3 returns an array of 3 items.
For this reason, map alone is not going to give you what you want. You may be able to map => reduce it. However, here is a way using forEach instead. This isn't a strictly functional programming style solution, but is pretty straight forward and depending on use case, probably good enough.
let keys = ['name','username', 'email'] //you have this array
const obj = {}; // empty object to hold result
keys.forEach(i => {
obj[i] = i; // set the object as you want
})
console.log(obj); // log out the mutated object
// { name: 'name', username: 'username', email: 'email' }
I am using Redis in my backend to scale subscriptions. I am using this library to implement redis on top of my javascript code. And using mongoose for the models.
During a redis publish, I have to stringify the objects that I get from mongoose. I parse them on the subscribing end and it all works well until there's a nested object in the object that needs to be stringify-ed.
So if my object is this:
{ subtitle: '',
description: '',
checklists:
[ { _id: 5cee450c0fa29d0b54275da0, items: [] },
{ _id: 5cee455c0c31785b0875e09d, items: [] },
{ _id: 5cee47dc6d32e72c6411ce2d, items: [] } ],
attachments: [],
labels: [],
_id: 5ced1af26547233798f943f6,
title: 'asfasf',
box: 5cece1c3e6c3c13ff098658d,
workflow: 5cece1cbe6c3c13ff0986591,
}
I receive:
{ cardUpdated:
{
subtitle: '',
description: '',
checklists: [ [Object], [Object], [Object] ],
attachments: [],
labels: [],
_id: '5ced1af26547233798f943f6',
title: 'asfasf',
box: '5cece1c3e6c3c13ff098658d',
workflow: '5cece1cbe6c3c13ff0986591',
}
}
When I publish I use the following line:
pub.publish(types.CARD_UPDATED,
JSON.stringify(
{ cardUpdated: await getUpdatedCardStats(checklist.card) },
));
Note: I know that I am wrapping the argument for stringify in {} and without it the nested objects would not be ignored, but I need to do that because I need the key property name on the subscription end i.e. I am using this publish command with different key names at several places.
Is there a way to about this to get the nested objects stringify-ed?
EDIT: Turns out, I was getting the proper full object as a string on the subscribing end of Redis, but it was actually JSON.parse() that was the culprit. After parsing, it completely ignores the nested objects. Is there anyway to avoid this?
Try:
const value = JSON.stringify({
cardUpdated: await getUpdatedCardStats(checklist.card)
});
pub.publish(types.CARD_UPDATED, value);
This is not a valid JS object:
{ _id: 5cee450c0fa29d0b54275da0, items: [] }
I think it's the output of .toString() of an object of type {_id: ObjectId, items: any[], with ObjectId defined here. In any case, the JSONification of this object is not trivial and that is why JSON.stringify simply outputs [Object].
To bypass this limitation, you might implement a custom function to transform your object into one that can be trivially JSONified, possibly with the help of ObjectId.toString().
I have an array with nested array
I want the data to append in a new array.
For the data extraction or filtration what method's i have to use, using library such as lodash
DATA
[
[
{
_id: 588d9b8a608f2a66c298849f,
email: 'sd#',
password: '$2a$10$6..L3c3tANi6ydt9gZbc1O6prPfUd3RB.ner5lilxRyEwo1lPsSoC',
isJobSeeker: true,
__v: 0,
lastName: 'shrestha',
firstName: 'manish',
isSeeker: true
}
],
[
{
_id: 588dbb4f7a48ce0d26cb99fd,
jobId: [Object],
seekerId: 588d9b8a608f2a66c298849f,
employerId: 588d7d6c0ec4512feb819825,
__v: 0,
}
]
]
REQUIRED DATA
[
{
_id: 588d9b8a608f2a66c298849f,
email: 'sd#',
password: '$2a$10$6..L3c3tANi6ydt9gZbc1O6prPfUd3RB.ner5lilxRyEwo1lPsSoC',
isJobSeeker: true,
__v: 0,
lastName: 'shrestha',
firstName: 'manish',
isSeeker: true
},
jobId: [{}, {}, {}] // ARRAY WITH OBJECTS
]
also i want to change the jobId key to other key of custom string as jobs
Following is my attempt:
console.log('Data filteration', data);
const filteredData = [];
filteredData.push(data[0][0]);
data[1].forEach((i) => {
filteredData[0].jobs = i.jobId
});
console.log('filteredData', filteredData);
First you should clean you data to have a better structure.
[
[
{ ... }
],
[
{ ... }
]
]
In this datastructure, its difficult to understand what does inner arrays signify. Instead you should use an object. That would define the purpose of array and make your code more readable.
var data=[[{_id:"588d9b8a608f2a66c298849f",email:"sd#",password:"$2a$10$6..L3c3tANi6ydt9gZbc1O6prPfUd3RB.ner5lilxRyEwo1lPsSoC",isJobSeeker:!0,__v:0,lastName:"shrestha",firstName:"manish",isSeeker:!0}],[{_id:"588dbb4f7a48ce0d26cb99fd",jobId:["test","test1"],seekerId:"588d9b8a608f2a66c298849f",employerId:"588d7d6c0ec4512feb819825",__v:0}]];
var cleanedData = {
userData: data[0],
userJobMap: data[1],
}
var result = cleanedData.userData.reduce(function(p,c){
if(c.isJobSeeker){
var job = cleanedData.userJobMap.filter(x=> x.seekerId === c._id);
// To copy object and not reference
var t = Object.assign({}, c, { jobId: job[0].jobId });
p.push(t)
}
return p
}, [])
console.log(result)
References
Array.map is a tool that iterates over all elements and return different value say a single property of return double value of all numbers in array. Note, this will yield an array of same size.
Array.filter on the other hand is use to filter array based on condition. This will return a subset of original data but elements will be same. You cannot change element structure.
Array.reduce is a tool that address cases where you need to return selected elements with parsed value. You can achieve same by chaining .filter().map() but then its an overkill as it would result in O(2n).
Object.assign In JS objects are passed by reference. So if you assign an object to a variable, you are not copying entire object, but only reference. So it you change anything in this variable, it will also reflect in original object. To avoid this, you need to copy value. This is where Object.assign comes. Note, its not supported by old browsers. For them you can check following post - What is the most efficient way to deep clone an object in JavaScript?
Note: All array functions are part of functional programming paradigm and are used to make your code more readable and concise but they come at an expense of performance. Traditional for will always perform faster then them. So if you want to focus on performance, always try to use for (though difference is very small but can add up for multiple cases and become substantial)
I would like to count all the companies in the following JSON string. I was first planning on doing it manually with loops but it seems like this is a good chance for me to learn to use map/reduce... How can return something that returns {company: 2}?
[
{
_id: '123',
company: 'Acme'
}
{
_id: '123',
company: 'Innatrode'
}
{
_id: '123',
company: 'Acme'
}
]
If you want to get the number of unique company names, then
use _.pluck to get the company attribute out of the list of company objects
Find the unique values out of them with _.uniq, which will return an array.
Compose a new object with the key `com
console.log({company: _.uniq(_.pluck(companies, "company")).length});
# { company: 2 }