We Keep Coding

Native JavaScript Way to Walk up Document Tree When Comparing Objects

I have done some work to do a deep comparison (via Underscore and diff) between two objects (actually a pre-save and post-save version of the same document) in order to isolate the section that is different after a save. Take this document structure as an example:
{
_id: 4d39fe8b23dac43194a7f571,
name: {
first: "Jane",
last: "Smith"
}
services: [
{
service: "typeOne",
history: [
{ _id: 121,
completed: true,
title: "rookie"
},
{ _id: 122,
completed: false,
title: "novice"
}
]
},
{
service: "typeTwo",
history: [
{ _id: 135,
completed: true,
title: "rookie"
},
{ _id: 136,
completed: false,
title: "novice"
}
]
}
]
}
If a new element is added to the history array I'm able to successfully parse out that change.
However, in addition to pulling out this changed section, I also want to be able to effectively walk up from history in order to find the value for service, because I also need to know which of the two services array elements actually changed. Is there a way I can do this with native es6 JavaScript?
If not, is there a library I can use to determine this? Right now I'm able to get the value for "service" via indexing:
if (diff.path[1] === 0) {
targetService = "typeOne";
} else if (diff.path[1] === 1) {
targetService = "typeTwo";
} else if (diff.path[1] === 2) {
targetService = "typeThree";
}
But from my understanding this isn't full proof, because there's no guarantee the order of elements within "services" couldn't change at some point. I suppose this indexing method could work if I could enforce the ordering of the elements within the services array. I'm just not sure if there's a way to do that (open to suggestions if it is possible).

deep-diff gives you the path to this change, something like this:
{
kind: 'N',
path: ['services', 1, 'history'],
// ... other properties
}
You can use this path to track the changed object:
tree.services[changes.path[1]].service // 'typeTwo'

pg-promise ColumnSet use Postgres functions with def property

I am using a ColumnSet and the helper.insert function for a multi row insert.
I have a table column where I want to use the Postgres Date/Time now() function.
const cs = new helpers.ColumnSet([
'lastname',
{
name: 'rental_date',
def: 'now()'
}
], { table: { table: 'book_rental', schema: 'public' } })
let rentals = [
{
lastname: 'Mueller'
},
{
lastname: 'Johnson'
}
]
let insert = helpers.insert(rentals, cs)
db.result(insert)
.then(data => res.json({ message: 'Ok!' }))
.catch(err => res.json({ message: 'Not ok!' }))
It seems to be working by using def: 'now()', but I want to make sure that I am using it the right way.
Edit:
Regarding the answer in the comment. I tried to do the insert manually and it looks like Postgres is converting the 'now()' string into the now() function.
INSERT INTO book_rental (lastname, rental_date) VALUES ('Mueller', 'now()');
To involve your answer, am I right that this should be the correct code then?
const cs = new helpers.ColumnSet([
'lastname',
{
name: 'rental_date',
mod: ':raw',
def: 'now()'
}
], { table: { table: 'book_rental', schema: 'public' } })

Your code doesn't look right, for the following reasons:
You want to use now() without any condition, but the def value is only used when the property doesn't exist in the source object (see Column). The init callback is what should be used instead to guarantee the right value override.
You return now() as an escaped string, while the query needs it as a raw-text string.
First, let's declare a reusable Raw Text string, as per Custom Type Formatting:
const rawText = text => ({toPostgres: () => text, rawType: true});
Then you can define the column like this:
{
name: 'rental_date',
init: () => rawText('now()')
}
And make sure you are using the latest version of pg-promise (v7.2.1 as of this writing).
Or alternatively, you can declare it like this:
{
name: 'rental_date',
mod: ':raw', // same as mode: '^'
init: () => 'now()'
}
This syntax however will work in all versions of the library, and perhaps is even simpler to use ;)

Why can't I see all JS object properties on a Mongoose document?

I'm writing a route in Express (Node.js) in which i pull some data from mongoose. Let's say that at some some point I need to compare if employee._id is in array of bad employees id::
let employees = await EmployeeModel.find().exec();
employees.forEach(function (employee) {
if (arrayOfBadEmployees.indexOf(employee._id) !== -1) {
employee.isBad = true;
}
});
console.log(employees);
console.log(employees[0].isBad);
and here's my output:
[ { __v: 0, name: 'Employee X', _id: 1 },
{ __v: 0, name: 'Employee Y', _id: 3 },
{ __v: 0, name: 'Employee Z', _id: 5 } ]
true
So when I can't see 'isBad' property when I console.log the whole array/object, but this property is still there? When i check with propertyIsEnumerable('isBad') it says true.

Mongoose, by default, returns an instance of MongooseDocument, which doesn't expose your data directly and adds convenience methods like populate or save
You can use the lean option to get raw objects instead.
MongooseDocument also exposes a toObject function if you need to get editable documents.

How to create a list of custom objects in GraphQL

I am currently playing around with a bunch of new technology of Facebook.
I have a little problem with GraphQL schemas.
I have this model of an object:
{
id: '1',
participants: ['A', 'B'],
messages: [
{
content: 'Hi there',
sender: 'A'
},
{
content: 'Hey! How are you doing?',
sender: 'B'
},
{
content: 'Pretty good and you?',
sender: 'A'
},
];
}
Now I want to create a GraphQL model for this. I did this:
var theadType = new GraphQLObjectType({
name: 'Thread',
description: 'A Thread',
fields: () => ({
id: {
type: new GraphQLNonNull(GraphQLString),
description: 'id of the thread'
},
participants: {
type: new GraphQLList(GraphQLString),
description: 'Participants of thread'
},
messages: {
type: new GraphQLList(),
description: 'Messages in thread'
}
})
});
I know there are more elegant ways to structure the data in the first place. But for the sake of experimenting, I wanted to try it like this.
Everything works fine, besides my messages array, since I do not specify the Array type. I have to specify what kind of data goes into that array. But since it is an custom object, I don't know what to pass into the GraphQLList().
Any idea how to resolve this besides creating an own type for messages?

You can define your own custom messageType the same way you defined theadType, and then you do new GraphQLList(messageType) to specify the type of your list of messages.

I don't think you can do this in GraphQL. Think that it's a bit against GraphQL philosophy of asking for the fields "you need" in each component against asking for "them all".
When the app scales, your approach will provoque higher loads of data. I know that for the purpose of testing the library looks a bit too much but it seems this is how it is designed. Types allowed in current GraphQL library (0.2.6) are:
GraphQLSchema
GraphQLScalarType
GraphQLObjectType
GraphQLInterfaceType
GraphQLUnionType
GraphQLEnumType
GraphQLInputObjectType
GraphQLList
GraphQLNonNull
GraphQLInt
GraphQLFloat
GraphQLString
GraphQLBoolean
GraphQLID

backbone.relational - key, keySource, keyDestination

I have the following two models: User and Job.
Each user can have just one job.
The user.attributes and job.attributes look like these (1):
(1)
user.attributes = {
id: 1,
name: 'barName',
job_id: 5
}
job.attributes = {
id: 5,
name: 'fooJob'
}
Let's suppose I want to make a relation between these two models:
The foreign key should be job_id
(2)
User = Backbone.ModelRelation.extend({
relations: [
{
type: Backbone.HasOne,
key: 'job_id',
keyDestination: 'job',
relatedModel: User
}
]
});
Using the code (2) the result will be:
(3)
user.attributes = {
id: 1,
name: 'barName',
job: job.attributes
}
As you can see the job_id from user.attributes is lost.
So, if I make a PUT request to the server, the server complains about the missing job_id attribute.
Any ideas how can I fix (3) in order to keep the job_id in user.attributes like (4)?
(4)
user.attributes = {
id: 1,
name: 'barName',
job_id: 5
job: job.attributes
}
Reference:
Paul Uithol - Backbone-relational

The workaround for me was to change the way the server reads the JSON posed.
So the server would read {user:{job:{id:1}}} rather than {user:{job_id:1}}
Note that we include a sub-object with an id attribute rather than use the job_id flat attribute.
Depending on which server side framework this can be configured.