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How to declare an array as a property of an object in an object constructor?

I'm trying to add an array as a property to an object in its constructor, like so:
let object {
entries = [],
}
But when I try to access the "entries" property, either inside a function of the object itself, or in an outside function, it isn't recognized as an array.

I think you just have a syntax error in constructing the object, there shouldn't be any issue accessing an array in an object:
let object = {
entries: [],
getEntries() {
return this.entries;
}
}
object.entries.push('it works');
console.log(object.entries)
console.log(object.getEntries())

mongdb/nodejs: using variables in $inc doesn't work

I have the following that i entered into the mongo terminal and it works great
db.cars.update({'_id':'FordXdfg'},{$inc :{'attribs.0.totl':1}})
which basically updates an array using dot notation, the 0 is the index of the array.
this does work. but transferring it to node my 0 comes from a variable.
so i tried
var carIndex = 3;
cars.update({'_id':'FordXdfg'},{$inc :{'attribs.' + carIndex + '.totl':1}}, function (err, callback) ................)
seems to be invalid javascript, if i replace my carIndex with 3 then it works i.e.
cars.update({'_id':'FordXdfg'},{$inc :{'attribs.3.totl':1}}, function (err, callback) ................)
Any ideas?
thanks

When using that style of object initialization in JavaScript, property names must be string literals. When using the object initialization syntax, property names can not be constructed at run time in code. For example, you can only use literals like:
{
"name": "Martin"
"location": "Earth"
"value": 1234
}
You cannot do this:
var propName = "name";
var obj = {
propName: "Martin";
};
While it syntactically appears to work, you'll end up with an object that looks like:
{
propName: "Martin"
}
Again, that's because only literal values are accepted when constructing an object using the shortened syntax. It will not interpret variable values.
There are two other options for setting properties of a JavaScript object, either through simple dot-notation:
obj.name = "Martin";
Or, you can use bracket notation:
obj["name"] = "Martin";
As objects in JavaScript act like associative arrays in that you can define new properties/keys at runtime each with a value, either syntax above works, and both result in the same underlying storage (and can be used interchangeably).
So, you'll need to construct the $inc syntax separately using the other technique for setting object property values in JavaScript:
var inc = {};
inc["attribs." + carIndx + ".totl"] = 1;
Then use that inside of your update:
{ $inc: inc }

How to refer to class using variable

If I have this object:
var myclass = {
foo: {
bar: function(var) {}
},
some: {
bar: function(var) {}
}
}
and I want to call the bar function depending on a variable that defines the parent level of the object like this:
var part = "some";
myclass.part.bar(var);
How can I do?

You can do it using array access notation:
myclass[part].bar(var);
JavaScript objects are like associative arrays, and you can use a property name to either set or get the property's value, you can even create new properties with this syntax.
For example:
var obj = { a : 1 };
console.log(obj["a"]); // 1
obj["b"] = 2; // this creates a property called b and assigns 2 as the value
console.log(obj["b"]); // 2

You can keep a reference to a function as a variable, which is a little cleaner than a string.
var func = myclass.foo.bar;//or myclass.some.bar
...
func.call(myclass, var);
Or keep a reference to the part:
var part = myclass.foo;//or myclass.some
part.bar.call(myclass, var);

How to declare nested objects in JavaScript?

I'm trying to create an object that contains an object, so think of it as a dictionary:
var dictionaries = {};
dictionaries.english_to_french =
{
{english:"hello",french:"bonjour"},
{english:"i want",french:"je veux"},
{english:"bla",french:"le bla"}
};
but it gives the error Uncaught SyntaxError: Unexpected token {
what am I doing wrong?
Thanks !
Edit
I'm sorry that I did not clarify what I want to do.
Edited the code above.

You're trying to give your object a property, and that property will be a single object:
dictionaries.english_to_french =
{english:"hello",french:"bonjour"}
;
You don't need the extra { }. You could declare the whole thing at once:
var dictionaries = {
english_to_french: {
english: "hello", french: "bonjour"
}
};
I would suggest that a better format for your dictionaries might be:
var dictionaries = {
english_to_french: {
"hello": "bonjour",
"chicken": "poulet", // ? something like that
"Englishman": "rosbif"
}
};
That way you can look up words directly without having to search. You could then create the reverse dictionary from that:
dictionaries.french_to_english = function(dict) {
var rv = {};
for (var eword in dict)
rv[dict[eword]] = eword;
return rv;
}(dictionaries.english_to_french);

In order to nest two or more objects, the objects need to have an attribute assigned to them. For example,
{
"hello":{
"english":"hello",
"french":"bonjour",
"portuguese":"ola"
},
"good day":{...},
"how are you":{...}
}
"hello" at the beginning of the object would be the attribute. Then the object is its value. So that way you can access the object by accessing its attribute. Just putting an object in an object does not work. That's why you're getting your error.

Class members in Backbone/Parse using each other

var User = Parse.User.extend({
// instance members
}, {
// types
TYPE_TRAINER : 1,
TYPE_ATHLETE : 2,
types: {
TYPE_TRAINER : 'Trainer',
TYPE_ATHLETE : 'Athlete'
}
});
I want to have TYPE_TRAINER and TYPE_ATHLETE maintain the values of 1 and 2 as defined prior to the types object so that I can use the types object in a template.
If you don't know about Parse, Parse.User is an extension of Backbone.Model.
Thanks!

What you're asking is not directly possible in JavaScript object literals. Object literals are always a literal value on the left hand / key side.
The closest you could get is to use the TYPE_TRAINER and TYPE_ATHLETE keys as variables to assign values via the square bracket syntax for accessing object key/value pairs:
var a = 1;
var b = 2;
var obj = {};
obj[a] = "a";
obj[b] = "b";
This will result in the obj object looking like this:
{
1: "a",
2: "b"
}
So you could do something like this, to get what you want in your code:
var userMethods = {
// types
TYPE_TRAINER : 1,
TYPE_ATHLETE : 2
};
userMethods[userMethods.TYPE_TRAINER] = 'Trainer';
userMethods[userMethods.TYPE_ATHLETE] = 'Athlete';
var User = Parse.User.extend({
// instance members
}, userMethods);
It's more code than you probably want, but it's the only way to achieve what you want because of the object literal syntax.

The Parse.Object Javascript documentation says:
You should call either:
var MyClass = Parse.Object.extend("MyClass", {
// Instance properties
}, {
// Class properties
});
or, for Backbone compatibility:
var MyClass = Parse.Object.extend({
className: "MyClass",
// Other instance properties
}, {
// Class properties
});
If you are wanting to extend the Parse.User "class" (it's an object, not a class), you need to include the className as described above because Parse.User is itself an extension of Parse.Object.