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How to render Array.length from inside of object to html page?

I am using jQuery and got an response from API by using $.ajax. I want to grab the Arrays length from inside each object and display that in the html page. This is what I have done so far.
Here is the API response, i did breakdown of the last object, which contains an array and player names:
{_type: "InjuredPlayers", flaggedTokens: Array(1)} //1 injured player name
{_type: "InjuredPlayers", flaggedTokens: Array(3)} //3 injured players names
{_type: "InjuredPlayers", flaggedTokens: Array(5)} //5 injured players names
{_type: "InjuredPlayers", flaggedTokens: Array(2)} //2 injured players names
>flaggedTokens:Array(2)
>0:{offset: 0, token: "John", type:"UnknownToken"}
>1:{offset: 1, token: "Adam", type:"UnknownToken"}
length: 2
>_proto_:Array(0)
_type: "InjuredPlayers"
>_proto_: Object
In order to grab the length of the Array I can do any of these 2 methods according to this Get length of array inside object
console.log(response.flaggedTokens.length)
1
3
5
2
OR
console.log(response["flaggedTokens"].length)
1
3
5
2
My Failed Attempts: I assigned this output to a variable and tried to loop through and output by doing this:
$.ajax(gameResponse).done(function(response) {
let injuredPlayers = response.flaggedTokens.length;
let injuredPlayersArray = [];
for (let i = 0; i < injuredPlayers.length; i++) {
injuredPlayersArray.push(injuredPlayers[i])
}
$('.injured_players').html(injuredPlayersArray[i])
})
<div class="container">
Team One Total number: <span class="injured_players"></span> //should be 1
Team Two Total number: <span class="injured_players"></span> //should be 3
Team Three Total number:<span class="injured_players"></span> //should be 5
Team Four Toal number: <span class="injured_players"></span> //should be 2
</div>
Clearly I made some mistake which I can't seem to figure this out by myself. I was hoping if someone can guide me through the right direction.

To start with, in your for loop, you are returning the push action, but that's unnecessary and it kills the loop on the first iteration. Also, you have already set the length of the array to a new variable, but then in your for loop, you try to get the length of the new variable. Lastly, you declare injuredPlayersArray in your ajax statement, but based on your post, you recieved 4 separate api responses, so it should be declared outside of your ajax call so that the array doesn't get overwritten with every new call. And you don't need a for loop as you're only working with one array. Here is what it should look like.
let injuredPlayersArray = [];
$.ajax(gameResponse).done(function(response) {
let injuredPlayers = response.flaggedTokens.length;
injuredPlayersArray.push(injuredPlayers)
})
Your other mistake is that you are trying to dynamically display the value in the proper html tag, but you're setting the value for every span tag at the same time. So after your loop is finished, they would all say 2.
To fix that you can add a for loop after all of your api calls are completed (aka NOT inside a $.ajax().done()):
for (let i = 0; i < injuredPlayersArray.length; i++) {
$('.injured_players').eq(i).html(injuredPlayersArray[i])
}
Note: .eq() returns a set of DOM elements that match the selector it is called upon. So $('.injured_players') matches 4 elements on your page and in your for loop, it finds the i-th element in that set (so index 0 is equal to the first span tag) and sets the html for that element.
Note 2: There is an assumption I had to make with your api calls. From the way your api call is storing the length of the flaggedToken array in your response, it seems each ajax response returns a single object with the array of injured players and that you will have 4 separate api calls. However, if that's not the case and the response returns a array of objects, you will need to iterate over the array and get the length for every array in every object one at a time. You can also then ignore my suggestion to move the declaration of injuredPlayersArray to outside the api call. And the second for loop i wrote would go inside the api call.

Is there a way to map a value in an object to the index of an array in javascript?

Prepending that a solution only needs to work in the latest versions of Chrome, Firefox, and Safari as a bonus.
-
I am trying to use an associative array for a large data set with knockout. My first try made it a true associative array:
[1: {Object}, 3: {Object},...,n:{Object}]
but knockout was not happy with looping over that. So I tried a cheating way, hoping that:
[undefined, {Object}, undefined, {Object},...,{Object}]
where the location in the array is the PK ID from the database table. This array is about 3.2k items large, and would be iterated over around every 10 seconds, hence the need for speed. I tried doing this with a splice, e.g.
$.each(data, function (index, item) {
self.myArray.splice(item.PKID, 0, new Object(item));
}
but splice does not create indices, so since my first PKID is 1, it is still inserted at myArray[0] regardless. If my first PK was 500, it would start at 0 still.
My second thought is to initialize the array with var myArray = new Array(maxSize) but that seems heavy handed. I would love to be able to use some sort of map function to do this, but I'm not really sure how to make the key value translate into an index value in javascript.
My third thought was to keep two arrays, one for easy look up and the other to store the actual values. So it combines the first two solutions, almost, by finding the index of the object in the first example and doing a lookup with that in the second example. This seems to be how many people manage associative arrays in knockout, but with the array size and the fact that it's a live updating app with a growing data set seems memory intensive and not easily manageable when new information is added.
Also, maybe I'm hitting the mark wrong here? We're putting these into the DOM via knockout and managing with a library called isotope, and as I mentioned it updates about every 10 seconds. That's why I need the fast look up but knockout doesn't want to play with my hash table attempts.
--
clarity edits:
so on initial load the whole array is loaded up (which is where the new Array(maxLength) would go, then every 10 seconds anything that has changed is loaded back. That is the information I'm trying to quickly update.
--
knockout code:
<!-- ko foreach: {data: myArray(), afterRender: setInitialTileColor } -->
<div class="tile" data-bind="attr: {id: 'tileID' + $data.PKID()}">
<div class="content">
</div>
</div>
<!-- /ko -->
Then on updates the hope is:
$.each(data.Updated, function (index, item) {
var obj = myModel.myArray()[item.PKID];
//do updates here - need to check what kind of change, how long it's been since a change, etc
}

Here is a solution how to populate array items with correct indexes, so it doesn't start from the first one (0 (zero) I meant)
just use in loop
arr[obj.PKID] = obj;
and if your framework is smart (to use forEach but not for) it will start from your index (like 500 in case below)
http://jsfiddle.net/0axo9Lgp/
var data = [], new_data = [];
// Generate sample array of objects with index field
for (var i = 500; i < 3700; i++) {
data.push({
PKID: i,
value: '1'
});
}
data.forEach(function(item) {
new_data[item.PKID] = item;
});
console.log(new_data);
console.log(new_data.length); // 3700 but real length is 3200 other items are undefined

It's not an easy problem to solve. I'm assuming you've tried (or can't try) the obvious stuff like reducing the number of items per page and possibly using a different framework like React or Mithril.
There are a couple of basic optimizations I can suggest.
Don't use the framework's each. It's either slower than or same as the native Array method forEach, either way it's slower than a basic for loop.
Don't loop over the array over and over again looking for every item whose data has been updated. When you send your response of data updates, send along an array of the PKIds of the updated item. Then, do a single loop:
.
var indexes = []
var updated = JSON.parse(response).updated; // example array of updated pkids.
for(var i=0;i<allElements.length;i++){
if(updated.indexOf(allElements[i].pkid)>-1)
indexes.push(i);
}
So, basically the above assumes you have a simple array of objects, where each object has a property called pkid that stores its ID. When you get a response, you loop over this array once, storing the indexes of all items that match a pk-id in the array of updated pk-ids.
Then you only have to loop over the indexes array and use its elements as indexes on the allElements array to apply the direct updates.

If your indexes are integers in a reasonable range, you can just use an array. It does not have to be completely populated, you can use the if binding to filter out unused entries.
Applying updates is just a matter of indexing the array.
http://jsfiddle.net/0axo9Lgp/2/

You may want to consider using the publish-subscribe pattern. Have each item subscribe to its unique ID. When an item needs updating it will get the event and update itself. This library may be helpful for this. It doesn't depend upon browser events, just arrays so it should be fairly fast.

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.

how do I create list of unique values and systematically store them in localstorage

I'm trying to build a history list of clicked clicked page elements and store that list into HTML local storage, to be later displayed back to the user. The main pre-requisite is that the list cannot contain duplicates, so for example if the user clicks on item A and then on item B and again back on item A, only A and B are recorded. The third click is not recorded because it is not unique.
I'm also using persist.js.
I noticed that I am able to name the storage and give it a key and both are stored together in the real key of the localstorage thus: myStorageName>myKeyand my value is whatever I put there.
Here's the thing. I know you can store stringyfied JSON there but my list is built up from simple javascript variables one at at time.
I know what to do for the first click:
myStorageName.set(myKey, myCurrentElementId); // myCurrentElementId = this.id
now on the second click this is where I'm beginning to getting stuck. There is the original variable value already stored, now I want to append the new variable value. Assume that I can get the value from the store like this:
var dataExtract = myStorageName.get(myKey);
myObject = JSON.parse(dataExtract);
But how do I then turn this into a JSONstring -able thing (sorry I don't even know what it should be) that contains only a list of unique values. Does this make any sense to anyone?

First of all, you don't want to keep writing to/from localStorage everytime a link is clicked, because this'll slow down your page. Keep an updated Array populated with the element ids, then write to localStorage before the user navigates away from the page (by binding to the window's onbeforeunload event, for instance).
First:
var clickedLinks = []; // this Array will hold the ids of the clicked links
function uniqueClick(id){
return !~clickedLinks.indexOf(id); // this tests whether the id is already in the Array
};
In your click handler:
if(uniqueClick(this.id)){
clickedLinks.push(this.id); // append the new element id to the Array
}
Bind to window.onunload to save the Array before the user navigates from the page:
window.onunload = function(){
localStorage.setItem('clickedLinks',JSON.stringify(clickedLinks)); // stringify the Array and save to localStorage
}
To retrieve clickedLinks on subsequent page visit:
// convert the String back to an Array; try/catch used here in case the value in localStorage is modified and unable to be parsed, in which case clickedLinks will be initialized to an empty Array
try{
var clickedLinks = JSON.parse(localStorage.getItem('clickedLinks')) || [];
}catch(e){
var clickedLinks = [];
}
You may want to replace the first line (var clickedLinks = [];) with this last bit of code, as it will initialize the Array if it doesn't exist.
UPDATE:
IE8 does not support Array.indexOf. Alternatives might be:
use jQuery's $.inArray by replacing !~clickedLinks.indexOf(id); with !~$.inArray(id, clickedLinks);
Detect whether Array.prototype.indexOf is supported. If not, shim it with the code provided on this page.

Your model has an error. At the first time, you save a primitive value. Then, you want to "append" another value to it. Seems like you actually want to use an object:
var myObj = localStorage.getItem("myName");
if(myObj) myObj = JSON.parse(myObj); //Variable exists
else myObj = {}; //Elsem create a new object
function appendNewValue(name, value){
myObj[name] = value;
localStorage.setItem("myName", JSON.stringify(myObj));
/* Saves data immediately. Instead of saving every time, you can
also add this persistence feature to the `(before)unload` handler. */
}

I suggest to define in your code this:
localStorage.set= function(key,val)
{
localStorage.setItem(JSON.stringify(val));
}
localStorage.get = function(key,defval)
{
var val = localStorage.getItem(key);
if( typeof val == "undefined" ) return defval;
return JSON.parse(val);
}
and use them instead of get/setItem. They will give you ready to use JS values that you can use in the way you need.