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Javascript's method forEach() creates array with undefined keys

I am building a simple todo app, and I'm trying to get the assigned users for each task. But let's say that in my database, for some reason, the tasks id starts at 80, instead of starting at 1, and I have 5 tasks in total.
I wrote the following code to get the relationship between user and task, so I would expect that at the end it should return an array containing 5 keys, each key containing an array with the assigned users id to the specific task.
Problem is that I get an array with 85 keys in total, and the first 80 keys are undefined.
I've tried using .map() instead of .forEach() but I get the same result.
let assignedUsers = new Array();
this.taskLists.forEach(taskList => {
taskList.tasks.forEach(task => {
let taskId = task.id;
assignedUsers[taskId] = [];
task.users.forEach(user => {
if(taskId == user.pivot.task_id) {
assignedUsers[taskId].push(user.pivot.user_id);
}
});
});
});
return assignedUsers;
I assume the issue is at this line, but I don't understand why...
assignedUsers[taskId] = [];
I managed to filter and remove the empty keys from the array using the line below:
assignedUsers = assignedUsers.filter(e => e);
Still, I want to understand why this is happening and if there's any way I could avoid it from happening.
Looking forward to your comments!

If your taskId is not a Number or autoconvertable to a Number, you have to use a Object. assignedUsers = {};

This should work as you want it to. It also uses more of JS features for the sake of readability.
return this.taskLists.reduce((acc, taskList) => {
taskList.tasks.forEach(task => {
const taskId = task.id;
acc[taskId] = task.users.filter(user => taskId == user.pivot.task_id);
});
return acc;
}, []);
But you would probably want to use an object as the array would have "holes" between 0 and all unused indexes.

Your keys are task.id, so if there are undefined keys they must be from an undefined task id. Just skip if task id is falsey. If you expect the task id to possibly be 0, you can make a more specific check for typeof taskId === undefined
this.taskLists.forEach(taskList => {
taskList.tasks.forEach(task => {
let taskId = task.id;
// Skip this task if it doesn't have a defined id
if(!taskId) return;
assignedUsers[taskId] = [];
task.users.forEach(user => {
if(taskId == user.pivot.task_id) {
assignedUsers[taskId].push(user.pivot.user_id);
}
});
});
});

Loop through 2 Arrays and assign a value from one array into each matching objects of second array

I have 2 Arrays 1.Options and 2.sameAccountArray
options.map((opt, optInd) => {
sameAccountArray.map((acObj, acInd) => {
if (opt.optNumber === acObj.optNumber) {
console.log(opt.optNumber, acObj.optNumber, acObj.exist, acObj.exist, 'WTF', sameAccountArray);
opt.exist = acObj.exist;
} else {
console.log(opt, acObj, opt.optNumber, acObj.optNumber, 'kundi');
// opt.exist = false;
}
// else {
// if (optInd === acInd) {
// opt.exist = acObj.exist;
// } else {
// console.log('elseeee', optInd, acInd,opt.optNumber, acObj.optNumber, opt.exist, acObj.exist);
// }
// }
});
});
Data Structure of sameAccountArray:
{
'key': key,
'shares': this.no_of_shares[key],
'refValue': this.your_reference[key],
'exist': false,
'accountNumber': extractedAccountNumber, 'optNumber': parseInt(extractedOptionNumber)
}
Option have big fields inside, but we don't need to care about it. options and sameAccountArray have common filed named optNumber. I am trying loop through each array and assign a value named exist in each object of the options array if optNumber is same. sameAccountArray already has the correct exist value, I just need to assign that value to match objects of options array. Somehow it's not assigned correctly. Please note that options array and sameAccount Array is not the same length. sameAccountArray has dynamic objects while options have a fixed number of elements. Any idea what is going wrong here guys? Thanks in advance

Try this:
options.forEach(opt=>{
sameAccountArray.forEach(acObj=>{
if (opt.optNumber === acObj.optNumber) opt.exist = acObj.exist;
})
})

The map() method creates a new array with the results of calling a provided function on every element in the calling array.
You cannot modify your arrays with map() function, but only create a new array with the results you want.

let sameAccountObject={};
sameAccountArray.forEach((account)=>{
sameAccountObject[account.optNumber]=account;
});
let result=options.map((option)=>{
let account=sameAccountObject[option.optNumber];
if(account){
option.exist=account.exist;
}
return option;
});
console.log(result);

Find texbox value match in an array

I am trying to look for texbox values matching an array I have provided a code snippet below:
$('#message').on('keyup', function () {
suggest_array_sample = [
{ array_val: "#{person1}" },
{ array_val: "#{person2}" },
{ array_val: "#{person3}" }
];
found_variable_array = [];
$.each(suggest_array_sample, function (key, value) {
console.log(value);
if ($.inArray(value, textbox_value)) {
console.log('found');
found_variable_array.push(value);
} else {
console.log('not found');
}
})
console.log(found_variable_array);
});
<textarea id="message"></textarea>
The problem is it always return the whole array instead of just the matches the ouput should be when I type #{person1} on the textbox the output should be
[{array_val:"#{person1}"}] //expected output
[{array_val:"#{person1}"},{array_val:"#person2"}]// expected output when two or more matches are found on the textbox
instead of
[{array_val:"#{person1}"},]{array_val:"#{person2}",{array_val:"#{person3}"}] //current output
is this possible using the inArray() or do I need to change the code.

use filter method of Array.
yourArray.filter ( yourArrayModel => yourArrayModel.fieldValue === yourSearchValue )
In your case yourSearchValue can be “{#person1}”
For more information, look for filter method documentation, i hope this is what you want.

$.inArray return a position, if not found return -1 else return >= 0
The $.inArray() method is similar to JavaScript's native .indexOf()
method in that it returns -1 when it doesn't find a match. If the
first element within the array matches value, $.inArray() returns 0
Try this code
$('#message').on('keyup', function () {
textbox_value = $(this).val();
suggest_array_sample = ["#{person1}", "#{person2}", "#{person3}"];
console.log($.inArray(textbox_value, suggest_array_sample));
});

It's not entirely clear what you're trying to achieve. I've written something using $.inArray that tells you the array index of the found value. You need to use .map() on the array to extract the val you want.
EDIT:
From what I understood of your comment, I've now had the value be added to found_value_array each time the value is found.
Or is it that you want an array to be returned because the same value might appear multiple times?
let found_variable_array = [];
$('#message').on('keyup',function(){
suggest_array_sample = [
{array_val:"#{person1}"},
{array_val:"#{person2}"},
{array_val:"#{person3}"}
]
let index = $.inArray($(this).val(), suggest_array_sample.map(o => o.array_val));
if (index >= 0) found_variable_array.push(suggest_array_sample[index]);
console.log(found_variable_array);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea id="message"></textarea>

After combining ideas presented here this method work for me
match_value = suggest_array.filter(function(result){
if(textbox_value){
return textbox_value.search(result)>-1
}
else{
return false
}
})
console.log(match_value);

Filter an array of nested objects

I have an array of nested objects and I have a user, which searches for a room
Here is an array of objects.
I would like to filter an array as soon as user types something
I tried a lot of functions, but nothing worked for me, here is the last example, which failed
search(val: any) {
// if input is clear - show everything, what we have
if (val === '') {
this.roomList = this.roomList;
} else {
//choose the object (objects) where rName = val
this.roomList = this.roomList.staticData.rName.filter(function(o) {
return Object.keys(o).some(function(k) {
return o[k].toString().toLowerCase().indexOf(val) != -1;
})
});
}
}
Could you please help or give me a hint?

You need to apply Array.filter() on roomList instead of staticData propety
this.roomList = this.roomList.filter(function (r) {
return r.staticData.rName.toLowerCase().indexOf(val.toLowerCase()) != -1
});

this.roomList = this.roomList.staticData.rName
This is a wrong starting point, just look at it. Then, rName is not an array, so you can't invoke .filter on it.
Here's how to do it :
this.roomListFiltered = this.roomList.filter(o => new RegExp(val,"i").test(o.staticData.rName) )
new RegExp(val,"i") performs a case-insensitive match.
Also, store the result of the filter in a different variable, otherwise you will lose your original list as it gets filtered out.

How to check if an Object already exists in an Array before adding it?

I have this algorithme issue, I would like to check if an Object is already present in my Array before adding it.
I tried many different approaches (indexOf, filter...), and my last attempt is with an angular.foreach.
The problem is my $scope.newJoin remains always empty. I understood why, it's because the if is never read, because of the 0 size of my $scope.newJoin, but I don't know how to figure this out...
$scope.newJoinTMP is composed by : 6 Objects, within each a timePosted attribute (used for compare these different array Objects).
$scope.newJoin is an empty Array. I want to fill it with the Objects inside $scope.newJoinTMP but with the certainty to have once each Objects, and not twice the same ($scope.newJoinTMP can have duplicates Objects inside, but $scope.newJoin mustn't).
angular.forEach($scope.newJoinTMP, function(item)
{
angular.forEach($scope.newJoin, function(item2)
{
if (item.timePosted === item2.timePosted)
{
//snap.val().splice(snap.val().pop(item));
console.log("pop");
}
else
{
$scope.newJoin.push(item);
console.log("newJoin :", $scope.newJoin);
}
});
});

if(!$scope.newJoin.find(el=>item.timePosted===el.timePosted){
$scope.newJoin.push(item);
console.log("newJoin :", $scope.newJoin);
}
You dont want to push inside an forEach, as it will push multiple times...

There might be better ways to handle your particular situation but here's a fix for your particular code.
Replaced your inner for each with some which returns boolean for the presence of element and by that boolean value, deciding whether to add element or not
angular.forEach($scope.newJoinTMP, function(item)
{
var isItemPresent = $scope.newJoin.some(function(item2)
{
return item.timePosted === item2.timePosted;
//you dont need this conditional handling for each iteration.
/* if (item.timePosted === item2.timePosted)
{
//snap.val().splice(snap.val().pop(item));
console.log("pop");
}
else
{
$scope.newJoin.push(item);
console.log("newJoin :", $scope.newJoin);
} */
});
if( ! isItemPresent ) {
$scope.newJoin.push(item);
} else {
//do if it was present.
}
});

If you want to avoid the nested loop (forEach, some, indexOf, or whatever) you can use an auxiliar object. It will use more memory but you will spent less time.
let arr = [{ id: 0 }, { id:0 }, { id: 1}];
let aux = {};
const result = arr.reduce((result, el) => {
if (aux[el.id] === undefined) {
aux[el.id] = null;
return [el, ...result];
} else {
return result;
}
}, []);
console.log(result);

You can use reduce
$scope.newJoin = $scope.newJoinTMP.reduce(function(c, o, i) {
var contains = c.some(function(obj) {
return obj.timePosted == o.timePosted;
});
if (!contains) {
c.push(o);
}
return c;
}, []);
The problem with your current code is, if newJoin is empty, nothing will ever get added to it - and if it isnt empty, if the first iteration doesn't match the current item being iterated from newJoinTMP - you're pushing.