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why console.log() creating /**id:4**/ and /**ref:4**/ values?

Few mins ago I did this answer and the answer snippet is below
let obj = {staff_changes: []};
let newStaff=[];
for (let i = 0; i < 4; i++) {
newStaff.push({id: 'staff' +i});
obj.staff_changes.push({
id: i,
newStaff: newStaff
});
}
console.log(obj);
If you run this above snippet, you can see /**id:4**/ and /**ref:4**/ . What is this?
When the code on execution time, that was pushing same duplicate values into a array. So I hope at the starting time it's generating a Id:4 and if the same duplicate value will exist, then just it write a comment like /**ref:4**/ where 4 means Id=:4 which is generated already.
So I want to know Is my understand is correct?. If my understanding is correct , then how can we avoid this? Shall I use object.assign() before push the value into array to avoid this?

Your data structure contains multiple references to the same object. console.log is intelligent enough to abbreviate the output.
Note that (AFAIK), the specification does not guarantee any particular output from console.log for objects that aren't instances of String, so you cannot rely on that output being the same across browsers, versions, phases of the moon, etc.
Consider an infinitely recursive data structure like const a = []; a.push(a); console.log(a), which one would you prefer: your computer to lock up while printing an infinitely recursive array or console.log abbreviating it?
const a = []
a.push(a)
console.log(a)
// [
// /**id:1**/
// /**ref:1**/
// ]

Depending on your console tools, they will display an object like this in different ways. Those comments are telling you there is more information deeper in the object.
If you want to see the internals in a consistent way, you can stringify the whole object
console.log(JSON.stringify(obj));
in which case you get:
{"staff_changes":[{"id":0,"newStaff":[{"id":"staff0"},{"id":"staff1"},{"id":"staff2"},{"id":"staff3"}]},{"id":1,"newStaff":[{"id":"staff0"},{"id":"staff1"},{"id":"staff2"},{"id":"staff3"}]},{"id":2,"newStaff":[{"id":"staff0"},{"id":"staff1"},{"id":"staff2"},{"id":"staff3"}]},{"id":3,"newStaff":[{"id":"staff0"},{"id":"staff1"},{"id":"staff2"},{"id":"staff3"}]}]}
In some developer tools, you can expand the object when you log it to the console, but the above string output shows you the whole lot consistently across tools.

How do I use #DbLookup results to populate a Readers field in xpages?

db = new Array("myserver", "myfolder\\mydb.nsf")
dir = getComponent("Dir").value;
div = getComponent("Div").value;
lu = #DbLookup(db, "ManagerAccess", dir + "PP" + div, "DTManagers");
var a = [];
a.push(lu);
var item:NotesItem = docBackEnd.replaceItemValue('FormReaders', #Unique(a));
item.setReaders(true);
That code is on the querySaveDocument ssjs. The result I get from the #DbLookup (when I put in a computed field) look like this:
Pedro Martinez,Manny Ramirez,David Ortiz,Terry Francona
I tried doing an #Explode(#Implode) thing on it, but it doesn't seem to work.
The error I get in the browser just tells me that the replaceItemValue line is broken.
To test it, I pushed several strings one at a time, and it worked correctly populating my FormReaders field with the multiple entries.
What am I doing wrong?

I see several problems here:
A. In cases as described by you #Dblookup in fact would return an array. If you push an array into a plain computedField control it will exactly look as that you wrote:
value1, value2, ..., valueN
A computedField doesn't know anything about multiple values etc, it just can display strings, or data that can be converted to strings.
If you want to test the return value you could try to return something like lu[0]; you then should receive the array's 1st element, or a runtime error, if lu is NOT an array. Or you could ask for the array's size using lu.length. That returns the number of array elements, or the number of characters if it's just a plain string.
B. your code contains these two lines:
var a = [];
a.push(lu);
By that you create an empty array, then push lu[] to the first element of a[]. The result is something like this:
a[0] = [value1, value2, ..., valueN],
i.e. a is an array where the first element contains another array. Since you don't want that, just use #Unique(lu) in your replaceItemValue-method.
C. I don't see why replaceItemValue would throw an error here, apart from what I wrote in topic B. Give it a try by writing lu directly to the item (first without #Unique). That should work.
D. for completeness: in the first line you used "new Array". A much better way to define your db parameters is
var db = ["myserver", "myfolder/mydb.nsf"];
(see Tim Tripcony's comment in your recent question, or see his blog entry at http://www.timtripcony.com/blog.nsf/d6plinks/TTRY-9AN5ZK)

How do I manipulate objects within arrays?

I've been given two arrays, each of which has several objects within them. I'm trying to make it so that when a certain dropdown selection is made, it pushes that "flight information" into a "flight summary" div, but I'm having a hard time figuring out how to do it.
var possibleDepartureFlights=[{year:2012,month:11,day:13,hour:17,minute:37,price:137.38} and so on];
var possibleReturnFlights=[{year:2012,month:11,day:18,hour:21,minute:45,price:189.46} and so on];
Each var has 10 objects within the array, each of which has all those properties.
And as a bonus question, I've figured out how to hide a "submit" button when the return flight selected is earlier than the departure, but I can't figure out how to make the submit button come back when a different selection is made!
function displayDivs() {
var departureValue = $('#departureFlightsControl').val();
var returnValue = $('#returnFlightsControl').val();
if (departureValue != "default") {
$('.CumulativeSummary').addClass('totalAvailable');
$('.DepartureSummary').addClass('flightChosen');
}
if (returnValue != "default") {
$('.CumulativeSummary').addClass('totalAvailable');
$('.ReturnSummary').addClass('flightChosen');
}
if ($('#returnFlightsControl').val() < $('#departureFlightsControl').val()) {
$('.SubmitArea').hide();
}
Sorry if this question is vague! I'm new to jQuery and JavaScript, so I'm not really sure what I'm doing (and I'm not even really sure what to Google for to find the answer to my problem(s)). Please use small words, as if you're speaking to a child. Thanks!

Your question is really too broad, anyways... Suppose you have following
var possibleDepartureFlights=[
{year:2012,month:10,day:13,hour:10,minute:37,price:137.38},
{year:2012,month:11,day:15,hour:17,minute:47,price:150.50}
];
The possibleDepartureFlights is an array of two objects and the first element of the array is the first object and it's {year:2012,month:10,day:13,hour:10,minute:37,price:137.38} and it's index is 0 and the second element in your possibleDepartureFlights array is the second object and it's {year:2012,month:11,day:15,hour:17,minute:47,price:150.50} and it's index is 1. Now, if you want to access the month property of the first item of the array then you can write like
alert(possibleDepartureFlights[0].month); // this will alert 10
For the month of the second item/object in the array you can write
alert(possibleDepartureFlights[1].month); // this will alert 11
To loop through the array and print out the each property of every objects, you can try this
for(i=0;i<possibleDepartureFlights.length;i++)
{
console.log(possibleDepartureFlights[i].year);
console.log(possibleDepartureFlights[i].month);
console.log(possibleDepartureFlights[i].hour);
console.log(possibleDepartureFlights[i].minute);
console.log(possibleDepartureFlights[i].price);
}
An Example Here.
Remember, this is only a short example and there are more about arrays and objects in JavaScript. Also remember that you can loop an object with for in like for loop. Also this one could be helpful too.

Javascript/jQuery Id check to drive numbering function with validation

I need help with a loop... it's probably simple but I'm having difficulty coding it up.
Basically, I need to check existing Ids for their number so I can create a unique id with a different number. They're named like this: id="poly'+i'" in sequence with my function where i is equal to the number of existing elements. Example: Array 1, Array 2, Array 3 corresponding with i=1 for the creation of Array 1, i=2 for Array 2, etc.
Right now i is based on the total number of existing elements, and my "CreateNew" function is driven off x=i+1 (so the example above, the new element will be named Array 4). The problem is that if you delete one of the middle numbers, the "Create" function will duplicate the high number. i.e. Array 1, 2, 3 delete 2, create new-> Array 1, 3, 3.
I need an if() statement to check if the array already exists then a for() loop to cycle through all i's until it validates. Not sure how to code this up.
The code I'm trying to correct is below (note I did not write this originally, I'm simply trying to correct it with my minimal JS skills):
function NewPanel() {
var i = numberOfPanels.toString();
var x = (parseInt(i)+1).toString();
$('#items').append('<div onclick="polygonNameSelected(event)" class="polygonName" id="poly'+i+'"> Array '+ x +' </div>');
$('div[id*=poly]').removeClass('selected');
$('#poly'+i).addClass('selected');
$('#poly'+i).click(function() {
selectedPolygon = i;
$('div[id*=poly]').removeClass('selected');
$(this).addClass('selected');
});
}
THANK YOU! :)

Please clarify "The problem is that if you delete one of the middle numbers, ". What do you mean by delete? Anyway, the simplest solution is to create two arrays. Both arrays will have the same created id's. Whenever an id is created in the first array, an id will be added to the second array. So when it is deleted from first array, check your second array's highest value and then create this id in first array. I hope this did not confuse you.

Well it is hard to tell why you cannot just splice the array down. It seems to me there is a lot of extra logic involved in the tracking of element numbers. In other words, aside from the index being the same, the ids become the same as well as other attributes due to the overlapping 1, 3, 3 (from the example). If this is not the case then my assumption is incorrect.
Based on that assumption, when I encounter a situation where I want to ensure that the index created will always be an appending one, I usually take the same approach as I would with a database primary key. I set up a field:
var primaryKeyAutoInc = 0;
And every time I "create" or add an element to the data store (in this case an array) I copy the current value of the key as it's index and then increment the primaryKeyAutoInc value. This allows for the guaranteed unique indexing which I am assuming you are going for. Moreover, not only will deletes not affect future data creation, the saved key index can be used as an accessor.

Does JavaScript populate empty array items?

I am coding a lot of annual data in JavaScript, and I was considering adding it to arrays, using the year as the array index and putting the data into the array. However, Firebug seems to be indicating that JavaScript handles this by populating two thousand odd entries in the array with "undefined." With hundreds of such arrays kicking around in active memory, I'm worried the overhead of hundreds of thousands of useless array items could start to slow the program down. Will it?

When you set the value of a numeric index higher than the current length of your array, the length property is affected.
In brief, you should use an Object:
var data = {};
data[year] = "some data";
// or
var data = {
2009: "2009 data",
2010: "2010 data"
};
Now I answer the question title: "Does JavaScript populate empty array items?"
No, as I said before, only the length property is changed, (if necessary, only if the index added is larger than the current length), length is incremented to be one more than the numeric value of that index.
The Array.prototype methods work assuming that the array object will have its indexes starting from zero.
The previous indexes don't really exist in the Array object, you can test it:
var array = [];
array[10] = undefined;
array.hasOwnProperty(10); // true
array.hasOwnProperty(9); // false
In conclusion, arrays are meant to contain sequential indexes, starting from zero, if your properties don't meet those requirements, you should simply use an object.

Yes, most likely. You should consider using a JavaScript object instead:
var years = {2009: 'Good', 2010: 'Better'};

Well, if you iterate over many thousands of undefined, it will affect overall program speed, not sure if you'll notice it though.

On the other hand, sometimes a sparse array is simpler to use than a custom object,
and arrays have such handy methods available.
In a calendar application I begin with objects for each year in use, but each year consists of a twelve member (months array) and each 'month' is a sparse array of significant dates, whose lengths depend on the highest date of that month that has any data.