Develop Reference

Adding another property with Key Value in an object

I am sorry if this question already asked but i guess it confusing so i want to know how to add a property in an object which is not defined in the object.
I want to add a property name: 'something' in a nested objects.
let cars = {
passengers: null,
engine: {
yearBuilt: 2002,
model: "25481 AL"
}
now it has two properties passengers and engine. What i want is to add another property "name" in passengers and log it in an array with ['Alex', 'Mark']
What i tried:
cars.passengers = [{name: 'Alex'}]; //Output is like this [ { name: 'Alex' } ],
and when i add a square bracket notation in Alex only the output will be
name: [Object] }
cars.passengers = [{name: 'Alex'}]; //Output is like this [ { name: ['Alex'] } ] //Output is like { passengers: [ { name: [Object] } ]
code:
let newData = cars.passengers = [{name: ['Alex']}];
why its not showing in an array.? and how to do that .?

Can u try
cars.passengers = {name: ['Alex'] }

Keys to Mongoose Object are different from property names

In order to troubleshoot an error I have been getting, I wrote the following snippet:
var myFunction = function(obj) {
var keys = Object.getOwnPropertyNames(obj);
console.log(obj);
console.log(keys);
}
When running my function within a mongoose query callback, the console logs this:
{_id: 5a8g123vjsdj83nf8afvn48,
username: 'Player1',
adv1: { name: 'a', type: '!' },
adv2: { name: 'a', type: '!' },
adv3: { name: 'a', type: '!' },
__v: 0,
invitations: [ 'PlayTest1', 'PlayTest2' ] }
[ '$__', 'isNew', 'errors', '_doc', '$init' ]
Now as far as I understand it, the last line in the console (separated for reading convenience) should read:
[ '_id', 'username', 'adv1', 'adv2', 'adv3', '__v', 'invitations ]
My question is why does the keys obj I create in myFunction not contain the properties names shown when I log the actual object?

Mongoose document fields are stored in obj._doc
console.log displays the document fields due to an .inspect function attached to the document object.
Use node --inspect if you want to debug something.

JS – How to build a dynamic nested object of arrays with objects etc. from string

This is a nice evening project, but actually i'm stuck with some headache.
All I need is a function like this example:
result = set("itemCategories[0].items[0].name", "Test")
which should return:
{ itemCategories: [
{
items: [ {name: "Test"} ]
}
}]
...and in case of the given attribute "itemCategories[1].items[2].name" this result:
{ itemCategories: [
null,
{
items: [
null,
null,
{name: "Test"}
]
}
}]

Use lodash#set:
result = lodash.set({}, "itemCategories[0].items[0].name", "Test")

If you are asking about the vanilla JavaScript Set method then you could do this.
/* this is what you are trying to get.
{ itemCategories: [
{
items: [ {name: "Test"} ]
}
}]
*/
var mySet = new Set(); // your set object.
Create your data (number, text, string, object, array, null).
ver data1 = 365;
ver data2 = 'Dragonfly';
ver data3 = {name: 'Bobby', age: 20000, job: 'dj'};
Then you just add to that set using its add method.
mySet.add(data1);
mySet.add(data2);
mySet.add(data3);
So to get what you are looking for you would write this.
var itms = {items: [{name: 'test'}]};
mySet.add(itms);
The good thing about set is that is like an array. So you can use forEach.
mySet.forEach( function(val){
console.log(val); // gets all your data.
});
You can even check if a value is in your data using the has method.
mySet.has(365); // true
mySet.has(36500000); as false
JavaScript Set

Get elements with biggest attribute using find only

EDIT: Ok, got it. It cannot be done with a find. I workarounded this in another way, but its pretty unrelated with this question: i added a boolean field "last_inserted" and used meteor hooks to make sure that only the last inserted have that field. Thank you all anyway.
I'm in a Meteor project and have a collection like this:
group_id, date, attribute1, attributeN
1, 2015-11-26 09:40:23.000Z, "foo", "bar"
1, 2015-11-23 14:23:53.000Z, "foo", "bar"
2, 2015-11-23 14:24:01.000Z, "foo", "bar"
2, 2015-11-23 14:25:44.000Z, "foo", "bar"
i have to filter this and get, for each group_id, the element with the biggest date, having a result like this:
group_id, date, attribute1, attributeN
1, 2015-11-26 09:40:23.000Z, "foo", "bar"
2, 2015-11-23 14:25:44.000Z, "foo", "bar"
I read in some related question that it can be done with the aggregate operator:
MongoDB - get documents with max attribute per group in a collection
but Meteor still doesn't implement it, and i have to do it with a find.
I'm no MongoDB expert and i'm reading the documentation from a lot, but i'm starting to fear that i can't do this without getting all the elements and manually filtering those in javascript (i really don't like this kind of solution)
I read there are some meteor packages that adds the aggregate command (like this), but i don't know how much they are reliable since this is a project that needs to be rock-solid
How can i do that?

This is a proposal in plain Javascript with a temporary object for the references to the result array.
var data = [{ group_id: 1, date: '2015-11-26 09:40:23.000Z', attribute1: 'foo', attributeN: 'bar' }, { group_id: 1, date: '2015-11-23 14:23:53.000Z', attribute1: 'foo', attributeN: 'bar' }, { group_id: 2, date: '2015-11-23 14:24:01.000Z', attribute1: 'foo', attributeN: 'bar' }, { group_id: 2, date: '2015-11-23 14:25:44.000Z', attribute1: 'foo', attributeN: 'bar' }],
result = function (data) {
var r = [], o = {};
data.forEach(function (a) {
if (!(a.group_id in o)) {
o[a.group_id] = r.push(a) - 1;
return;
}
if (a.date > r[o[a.group_id]].date) {
r[o[a.group_id]] = a;
}
});
return r;
}(data);
document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

How to filter objects with another object in Angular?

Working on a font library, I store fonts like this:
var fonts = [
{
name: "Foo",
style: "Bar",
families: [
{ name: "A", parent: "B" },
{ name: "C", parent: "D" }
]
} // and so on...
];
And I want to filter out fonts whose families list contains { name: "A", parent: "B" }.
The filter looks like var selection = [{ name: "A", parent: "B" }]
Actually, the code look like this:
// Triggers when a new family is added to the filter
$scope.$on('filter:changed', function(e, selection) {
_.each($scope.fonts, function(font) {
_.each(font.families, function(family) {
_.each(selection, function(item) {
if(_.isMatch(family, item)) {
console.log('font', font);
console.log('has a match for family', family);
} else {
console.log('no match for family', family);
}
});
});
});
});
What is the best way to do it without performance impact, as there will be thousands font objects in the future?

underscore#where
$scope.$on('filter:changed', function(e, selection) {
var multiselection,
singleSelection;
_.each($scope.fonts, function(font) {
multiselection = _.where(font.families, { name: "A", parent: "B" }); //all matching objects
singleSelection = _.findWhere(font.families, { name: "A", parent: "B" }); // single matching object
});
});
JSFIDDLE

Since you're using underscore use filter
From underscore docs:
_.filter(list, predicate, [context]) Alias: select Looks through each value in the list, returning an array of all the values that pass a
truth test (predicate).
So your filter would be (use this only if you want to manipulate data for each object, otherwise use where):
var myFamilyMatch = { name: "A", parent: "B" };
var selection = _.filter(fonts, function(font){
return _find(font.families, function(family){
return family == myFamilyMatch;
};
});
Or simply (and better) use where as #dcodesmith suggested:
_.where(list, properties) Looks through each value in the list, returning an array of all the values that contain all of the key-value
pairs listed in properties.
Underscore will take care of performance for you, so don't worry about it.