Develop Reference

Destructuring object with inner array without all keys

I have an object like this:
const objBefore:
{
"id": "3pa99f64-5717-4562-b3fc-2c963f66afa1",
"number": "5000",
"enabled": true,
"classes": [
{
"id": "2fc87f64-5417-4562-b3fc-2c963f66afa4",
"name": "General"
},
{
"id": "7ffcada8-0215-4fb0-bea9-2266836d3b18",
"name": "Special"
},
{
"id": "6ee973f7-c77b-4738-b275-9a7299b9b82b",
"name": "Limited"
}
]
}
Using es6, I want to grab everything in the object except the name key of the inner classes array to pass it to an api.
So:
{
"id": "3pa99f64-5717-4562-b3fc-2c963f66afa1",
"number": "5000",
"enabled": true,
"classes": [
{"id": "2fc87f64-5417-4562-b3fc-2c963f66afa4"},
{"id": "7ffcada8-0215-4fb0-bea9-2266836d3b18"},
{"id": "6ee973f7-c77b-4738-b275-9a7299b9b82b"}
]
}
The closest I got was: let {id, number, enabled, classes: [{id}]} = objBefore;
But it only gets me one id in classes. I've tried spreading above using [...{id}] or [{...id}]. Same thing.
I find it challenging to get the right mental model for how to think about this when it's on multiple levels. In my mind, when I say [...{id}] I'm thinking, "I want the id property as an object in the outer classes array, but give me every id in the array!"
Clearly I'm not thinking about this correctly.
I've tried it using map to get that part but I'm still having trouble combining it back to the original to produce the desired result. for example:
let classIds = objBefore.classes.map(({id}) => {
return {
id
}
})
(Using the map syntax, how can I destructure in the function the other keys that are one level higher?)
To combine them I started trying anything and everything, :
let {id, number, enabled, classIds} = {objBefore, [...classIds]} // returns undefined for all
I'd prefer to do it in one statement. But if that's not possible, then what's a clean way to do it using map?.

You can't destructure and map at the same time in the way you're looking to do it. The main purpose of destructuring assignment is to extract data from an array/object and not for manipulating data. In your case, as you're after an object with the same keys/value as your original object, just with a different classes array, I would instead suggest creating a new object and spreading ... the original object into that. Then you can overwrite the classes array with a mapped version of that array:
const objBefore = { "id": "3pa99f64-5717-4562-b3fc-2c963f66afa1", "number": "5000", "enabled": true, "classes": [ { "id": "2fc87f64-5417-4562-b3fc-2c963f66afa4", "name": "General" }, { "id": "7ffcada8-0215-4fb0-bea9-2266836d3b18", "name": "Special" }, { "id": "6ee973f7-c77b-4738-b275-9a7299b9b82b", "name": "Limited" } ] };
const newObj = {
...objBefore,
classes: objBefore.classes.map(({id}) => ({id}))
};
console.log(newObj);

How about using simple util method with object destructuring, spread operator and map
const objBefore = {
id: "3pa99f64-5717-4562-b3fc-2c963f66afa1",
number: "5000",
enabled: true,
classes: [
{
id: "2fc87f64-5417-4562-b3fc-2c963f66afa4",
name: "General",
},
{
id: "7ffcada8-0215-4fb0-bea9-2266836d3b18",
name: "Special",
},
{
id: "6ee973f7-c77b-4738-b275-9a7299b9b82b",
name: "Limited",
},
],
};
const process = ({ classes, ...rest }) => ({
...rest,
classes: classes.map(({ id }) => ({ id })),
});
console.log(process(objBefore))

In one line, you could do this:
const objAfter = { ...objBefore, classes: objBefore.classes.map(item => ({ id: item.id })) };
Or, if you prefer:
const objAfter = {...objBefore, classes: objBefore.classes.map(({id}) => ({id}))};
There isn't any way in object destructing to copy an entire array of objects into a different array of objects by removing properties so you use .map() for that.

React element - array objects only returning first item?

I am trying to retrieve item values from an object containing several items. The object is an array object. I am puzzled by only being able to retrive the first item and its values in each array instead of all items. Can anybody tell me what I am missing here.
The array object example:
{ "ITEM 1": [
{
"id": 123,
"name": "item1a"
},
{
"id": 234,
"name": "item1b"
},
{
"id": 345,
"name": "item1c"
}
],
"ITEM 2": [
{
"id": 456,
"name": "item2a"
},
{
"id": 567,
"name": "item2b"
},
{
"id": 678,
"name": "item2c"
}],
}
I have data within the new element and on debugging see that loop flows correctly but for some reason only the first item is rendered.
My code that is wrapped in an html element is as follows:
{ Object.keys(this.props.data).map(function (key) {
var list = component.props.data[key];
for (i = 0; i < facetParent.length; i++) {
var item = list[i];
return (
<CheckBox
key={item.id}
data={item}
name={item.name} />
)
}}, this)}
Any suggestions are much appreciated.

The return function immediately terminates the function execution. That is why you only get the first item. Depending on what version of react you use, you should create 2 arrays and join them before rendering

Deep picking using Underscore.JS

I am trying to use underscoreJs to manipulate a JavaScript object and having problems doing so.
Here is my example
var data = {
"label": "SomeName",
"parent": [{
"id": "parentId",
"resources": [{
"name": "ID1NAME",
"calls": [
"user_get", "user2_post", "user3_delete"
]
}, {
"name": "ID2",
"calls": [
"employee1_get", "employee2_delete", "employee3_update"
]
}]
}]
};
var res = _(data).chain().
pluck('parent').
flatten().
findWhere(function(item){
item === "user_get"
}).
value();
console.log(res);
Using an element which is a part of data.parent.calls[] (example : "user_get") I would like to extract its parent object, i.e. data.parent[0].
I tried above but always get undefined. I appreciate any help on this.

One of the problems you're having is your use of _.pluck. If you execute _.pluck over an object, it'll go over the keys of the object trying to retrieve the property you specified as the second argument (in this case, 'parent'). 'label' is a string and 'parent' is an array so thus the array that you get as a result is [undefined, undefined]. The rest will then go wrong.
One solution could be as follows:
function findCallIndexInParent(call, parent) {
return _.chain(parent)
.pluck('resources')
.flatten()
.findIndex(function (obj) {
return _.contains(obj.calls, call);
})
.value();
}
function findCall(call, data) {
var parent = data.parent;
return parent[findCallIndexInParent(call, parent)];
}
console.log(findCall('user_get', data));
findCall is just a convenient method that will pass the parent property of data to findCallIndexInParent (that will retrieve the index where call is) and return the desired object with the parent array.
Lodash (a fork of underscore) provides a method to get the property of an object that would have come really handy in here (sadly, underscore doesn't have it).
The explanation of findCallIndexInParent is as follows:
Chain the parent list
pluck the resources array
As pluck maps, it returns a list of lists so a flatten is needed.
Find the index of the element which calls contains call
Return the value (the index) of the object that contains call within parent.
Here's the fiddle. Hope it helps.

This would seem to do the trick.
function findByCall(data, call) {
return _.find(data.parent, function(parent) { //From data.parent list, find an item that
return _.some(parent.resources, function(resource) {//has such parent.resource that it
return _.includes(resource.calls, call); //includes the searched resource.calls item
});
});
}
//Test
var data = {
"label": "SomeName",
"parent": [{
"id": "parentId",
"resources": [{
"name": "ID1NAME",
"calls": [
"user_get", "user2_post", "user3_delete"
]
}, {
"name": "ID2",
"calls": [
"employee1_get", "employee2_delete", "employee3_update"
]
}]
}]
};
console.log(findByCall(data, 'user_get'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore.js"></script>

If I understand correctly, you want to get the index of the element in the parent array which has any resource with the specified call.
data = {
"label": "SomeName",
"parent": [{
"id": "parentId",
"resources": [{
"name": "ID1NAME",
"calls": [
"user_get", "user2_post", "user3_delete"
]
}, {
"name": "ID2",
"calls": [
"employee1_get", "employee2_delete", "employee3_update"
]
}]
}]
}
// find the index of a parent
const index = _.findIndex(data.parent, parent =>
// that has any (some) resources
_.some(parent.resources, resource =>
// that contains 'user_get' call in its calls list
_.contains(resource.calls, 'user_get')
)
)
console.log(index) // 0
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>
If you want to find the actual parent object, use find instead of findIndex
If you want to find all parent objects matching this call, use filter instead of findIndex

Mapping and binding nested objects and arrays

I have an object and within this object I have items and one of the items is an array which also contains objects. A sample of the data is shown below.
I am using knockout to bind this data to the view so I think I need to implement a double loop for returning the objects and the objects within the child array to be able to bind them in the view.
Sample data:
"singers": {
"ijiyt6ih": {
"id": ObjectId('ijiyt6ih'),
"name": "John",
"songs": [
{
"id": ObjectId('okoiu8yi'),
"songName": "Hello There",
"year": "1980"
},
{
"id": ObjectId('sewfd323'),
"songName": "No More",
"year": "1983"
}
]
},
"98usd96w": {
"id": ObjectId('98usd96w'),
"name": "Jack",
"songs": [
{
"id": ObjectId('iew342o3'),
"songName": "Hurry Up",
"year": "1985"
}
]
}
}
I need to find a way to appropriately loop through this so that I can modify the returned data to bind it to the viewModel using knockout.
Here is how my viewModel looks like:
singersViewModel = function(data) {
var self = {
singerId: ko.observable(data.id),
singerName: ko.observable(data.name),
songName: ko.observable(...),
songYear: ko.observable(...)
};
I am not sure if I will have to return two different sets of data or not.
As for the looping. I was able to loop and return the list of singers to display on the page but I am not able to get the list of songs displayed within each singer.
Here is my loop so far:
var self = {},
singer,
tempSingers = [];
self.singers = ko.observableArray([]);
for (singer in singers) {
if (singers.hasOwnProperty(singer)) {
tempSingers.push(new singersViewModel(singers[singer]));
}
}
self.singers(tempSingers);
I tried to duplicate the same type of loop for songs within this loop but i would get an error using hasOwnProperty because songs is an array.

In the included snippet you can see how you can map the original data to a viewmodel that can be bound to a view.
I've left the ids as regular properties, and converted the names into observables, so thatthey can be edited. At the bottom you can see the current viewmodel state.
There is also a sample view which iterates the list of singers, and also the list of song within each singer.
As you can see I'm implementing the solution using mapping. For mapping you need to implement a callback that receives each original object and returns a new one with a new structure. For example this part of the code
_.map(_singers, function(singer) {
return {
id: singer.id,
name: ko.observable(singer.name),
// ... songs:
})
iterates over each singer (the sample data in the question), and for each one creates a new object with the id, an observable which includes the name (and the mapping of songs, which I don't show in this fragment).
NOTE: I'm using lodash, but many browsers support map natively as an array function
var ObjectId = function (id) { return id; }
var singers = {
"ijiyt6ih": {
"id": ObjectId('ijiyt6ih'),
"name": "John",
"songs": [
{
"id": ObjectId('okoiu8yi'),
"songName": "Hello There",
"year": "1980"
},
{
"id": ObjectId('sewfd323'),
"songName": "No More",
"year": "1983"
}
]
},
"98usd96w": {
"id": ObjectId('98usd96w'),
"name": "Jack",
"songs": [
{
"id": ObjectId('iew342o3'),
"songName": "Hurry Up",
"year": "1985"
}
]
}
};
var SingersVm = function(_singers) {
var self = this;
self.singers = _.map(_singers, function(singer) {
return {
id: singer.id,
name: ko.observable(singer.name),
songs: _.map(singer.songs, function(song) {
return {
name: ko.observable(song.songName),
id: song.id
};
})
};
});
return self;
};
var vm = new SingersVm(singers);
//console.log(vm);
ko.applyBindings(vm);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.10.1/lodash.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div data-bind="foreach: singers">
<div>
<input data-bind="value: name"/> (<span data-bind="text: id"></span>)
<ul data-bind="foreach:songs">
<li>
<input data-bind="value: name"/> (<span data-bind="text: id"></span>)
</li>
</ul>
</div>
</div>
<pre data-bind="html: ko.toJSON($root,null,2)">
</pre>

How do I chain "SelectMany" calls with linqjs (or flatten JSON)

Using linq.js how can I chain two SelectMany calls together.
Given the following JSON structure:
[
{
"UpFrontCost": "29.95",
"Currency": "USDAUD",
"FittingDate": "2013-07-08 06:30:16Z",
"Widgets": [
{
"ID": 3,
"Name": "Test1"
},
{
"ID": 4,
"Name": "Test19"
},
{
"ID": 6,
"Name": "Test8"
}
]
},
{
"UpFrontCost": "29.95",
"Currency": "USDAUD",
"FittingDate": "2013-07-08 06:30:16Z",
"Widgets": [
{
"ID": 67,
"Name": "Test1"
},
{
"ID": 99,
"Name": "Test19"
},
{
"ID": 34,
"Name": "Test8"
}
]
}
]
I would like a list of all the "Widgets" (in this example a list of 6 widgets).

You don't need to really chain anything. Your root object is an array, you just want to select each widget for each object in that array.
var query = Enumerable.From(jsonObject)
.SelectMany("$.Widgets") // Select each widget found in the Widgets property
.ToArray();
To flatten that array of widgets attaching each property of the parent object to the result, there's a couple of ways you could do it. You can use a nested query using the function syntax.
var query = Enumerable.From(jsonObject)
.SelectMany(function (item) {
return Enumerable.From(item.Widgets)
.Select(function (widget) {
return {
ID: widget.ID,
Name: widget.Name,
UpFrontCost: item.UpFrontCost,
Currency: item.Currency,
FittingDate: item.FittingDate
};
});
})
.ToArray();
Or using the lambda string syntax:
var query = Enumerable.From(items)
.SelectMany("$.Widgets",
// argument 1 ($) - the parent object
// argument 2 ($$) - the selected object (a widget)
"{ ID: $$.ID, Name: $$.Name, UpFrontCost: $.UpFrontCost, Currency: $.Currency, FittingDate: $.FittingDate }"
)
.ToArray();