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Remove singular element from an object's key array

I have an object that has multiple keys and each of these keys has an array storing multiple elements. I want to be able to remove a specified element from the key's array.
I have tried using the delete keyword as well as the filter method, but I have been unsuccessful. I'm a total newbie to JS so I appreciate any assistance. Also, I want to do this using ONLY JavaScript, no libraries.
Here is the code where I am creating my object:
function add(task, weekdayDue) {
let capitalWeekday = weekdayDue.charAt(0).toUpperCase() +
weekdayDue.slice(1);
if (toDoList[capitalWeekday] === undefined) {
let subArr = [];
toDoList[capitalWeekday] = subArr.concat(task);
} else {
toDoList[capitalWeekday].push(task);
}
}
and here is the code as I have it now. Clearly it is not producing the correct result:
function remove(task, weekdayDue) {
let capitalWeekday = weekdayDue.charAt(0).toUpperCase() +
weekdayDue.slice(1);
delete toDoList.capitalWeekday[task]
//the below code is working; i want to send this to another
array
if (archivedList[capitalWeekday] === undefined) {
let subArr = [];
archivedList[capitalWeekday] = subArr.concat(task);
} else {
archivedList[capitalWeekday].push(task);
}
};
add('laundry', 'monday');
add('wash car', 'monday');
add ('vacuum', 'tuesday');
add('run errands', 'wednesday');
add('grocery shopping', 'wednesday');
// the output is: { Monday: [ 'laundry', 'wash car' ],
Tuesday: [ 'vacuum' ],
Wednesday: [ 'run errands', 'grocery shopping' ] }
Then let's say I want to remove 'wash car' from Monday I was trying:
remove('wash car', 'monday');
console.log(toDoList)
// The output is an empty object {}

I personally would refactor a bit your code, but I've worked a bit around it to fix some issues.
First of all, you shouldn't use delete for your scenario, because it will reset the item at the nth position of the array with the default value, which is undefined.
Usually, for that kind of operations, since you deal with strings, you rather take a look at the first occurrence of your item in the array, take its index, and use splice (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice) to actually remove the item from the array.
In this way, you end up with a clean array without invalid items in it.
Below is the working code (with the mentioned fixes) that does what you asked. As a side note, I would suggest you to avoid working with strings for such purposes, but I would rather tackle objects with unique ids, so that it's significantly easier to keep track of them between arrays and objects.
Additionally, there are some cases that you didn't think about, for instance I can think about calling remove by giving an invalid task, so you may work a bit around the code below to handle the case where taskIndex is -1 (meaning that no item was found with that index).
var toDoList = {}, archivedList = {};
function add(task, weekdayDue) {
let capitalWeekday = weekdayDue.charAt(0).toUpperCase() + weekdayDue.slice(1);
if (toDoList[capitalWeekday] === undefined) {
let subArr = [];
toDoList[capitalWeekday] = subArr.concat(task);
} else {
toDoList[capitalWeekday].push(task);
}
}
function remove(task, weekdayDue) {
let capitalWeekday = weekdayDue.charAt(0).toUpperCase() + weekdayDue.slice(1);
let taskIndex = toDoList[capitalWeekday].indexOf(task);
toDoList[capitalWeekday].splice(taskIndex, 1);
//delete toDoList[capitalWeekday][taskIndex];
if (archivedList[capitalWeekday] === undefined) {
let subArr = [];
archivedList[capitalWeekday] = subArr.concat(task);
} else {
archivedList[capitalWeekday].push(task);
}
};
add('test', 'monday');
add('wash car', 'monday');
remove('wash car', 'monday');
console.log(toDoList);
console.log(archivedList);

You are on the right path. Maybe the trouble you had with filter is because filter will return a new Array and not modify the current one. You could update your remove function and replace the line:
delete toDoList.capitalWeekday[task]
with
toDoList.capitalWeekday = toDoList.capitalWeekday.filter((item) => {return item !== task});

function remove(task, weekdayDue) {
let capitalWeekday = weekdayDue.charAt(0).toUpperCase() +
weekdayDue.slice(1);
// Assign new array with all elements but task
toDoList[capitalWeekday] = toDoList[capitalWeekday].filter(i => i !== task)
};
add('foo'...
add('bar'...
"{
"Baz": [
"Foo",
"Bar"
]
}"
remove('foo'...
"{
"Baz": [
"Bar"
]
}"

Improve loop over nested properties - javascript

Trying to filter students according to a nested property value.
Basically each student object has property of type array : studentSuperSubject
which in turn has array as a property as well : studentSubSubjectOrSkill
subjects is array of objects in the following form:
{superSubject: "some super subject name", subSubject: "some sub subject name"}.
each subSubject inside studentSubSubjectOrSkill has the property studentSubSubjectScore which is the one I'm looking for.
I want to loop over the students array for each subject in subjects and create and object i then store to another array - grades=[]
I manage to get it done with what looks like a Hugh bawl of spaghetti code:
for (let subject of subjects) {
var grades = [];
this.data.students.filter(student => {
let name = student.studentName;
// loop over each student > superSubject > subSubject
for (let superSubject of student.studentSuperSubject) {
if (superSubject.superSubjectName === subject.superSubject) {
superSubject.studentSubSubjectOrSkill.filter(sub => {
if (sub.subSubjectName === subject.subSubject) {
grades.push({
name: name,
pass: sub.studentSubSubjectScore > 58
});
return;
}
});
}
}
});
subject["grades"] = grades;
}
Any idea how can I improve that to make life easier for the future developers which are going to use this code?
as a side note, lodash is available in this project
thanks.

1/ You have improper use of filter that should be used when you want to return subset of the array, you should use map when you want to execute an action for each element of the array
2/ for... of ... is for iterating over the values, for... in... over the properties
3/ I think it is more readable like this:
for (let subject of subjects) {
var grades = [];
this.data.students.map(student => {
let name = student.studentName;
student.studentSuperSubject
.filter(superSubject => superSubject.superSubjectName === subject.superSubject)
.map(superSubject=> {
superSubject.studentSubSubjectOrSkill
.filter(sub => sub.subSubjectName === subject.subSubject)
.map(sub=>{
grades.push({
name: name,
pass: sub.studentSubSubjectScore > 58
});
});
});
});
subject["grades"] = grades;
}

For readability, I would check one thing at a time and add some comments.
// Iterates for all subjects.
subjects.forEach(subject => {
// Subject grades.
subject.grades = [];
// Iterates for all the students.
students.forEach(student => {
// Finds and validates the student super subject.
var studentSuperSubject = student.studentSuperSubject.find(superSubject => superSubject.superSubjectName === subject.superSubject);
if (!studentSuperSubject) return;
// Finds and validates the student sub subject.
var studentSubSubject = studentSuperSubject.studentSubSubjectOrSkill.find(subSubject => subSubject.subSubjectName == subject.subSubject);
if (!studentSubSubject) return;
// Saves the student grade.
subject.grades.push({
name: student.studentName,
pass: studentSubSubject.studentSubSubjectScore > 58
});
});
});

Adding only Distinct numbers during map reduce

I have a csv as to which number called which number and the call details(duration and time etc.)
i want to have all the numbers a particular number called in an array.
that array should be an array of documents and so,in each document i can have all the call details also.
so finally i need documents with a "caller" number and a "called" array(that array is as defined above).
for this i had come up with a map reduce solution.(quite basic and intuitive).
but my problem is that i need only distinct numbers that a "caller" number has called.
my current mapreduce script repeats the dialled numbers.
how can i only consider unique numbers during the reduce phase?
my code looks like this:(i enter this in the mongo shell)
db.contacts.mapReduce(
function(){
numbers = [];
value={phone:this.<<called_number>>};
numbers.push(value);
emit(this.<<caller_number>>,{called:numbers});
},
function(key,values) {
result={called:[]};
values.forEach(function (v) {
var i,j;
for(i=0;i<v.called.length;i++) {
var flag=0;
for(j=0;j<result.called.length;j++) {
if(v.called[i].phone==result.called[j].phone){
flag=1;
}
}
if(flag==0) {
result.called.push(v.called[i])
}
}
});
return result;
},
{"query": {},"out":"new_collection"}
)
I understand that the map and reduce functions are java script functions.
so even the javascript coders can help me out here(to create the reduce function).

Try this.
db.contacts.mapReduce(function(){
emit(this.<<caller_number>>, {called:this.<<called_number>>, callDuration:this.<<callDuration>>,...});}
,function(key,values)
{
var map = {};
var called=values.filter(function removeDuplicated(it){
if (!map[it.called]){
map[it.called] = 1;
return true;
}
return false;
})
return {caller:key, called:called};},
{"query": {},"out":"new_collection"})

Access the nested value in JSON without looping through it

This is my JSON, I want to directly get the zipCodes values from the JSON without looping through the JSON. How can I do it?
countries:[
{
name:'India',
states:[{
name:'Orissa',
cities:[{
name:'Sambalpur',
zipCodes:{'768019','768020'}
}]
}]
}
]

I think you are looking for
countries[0].states[0].cities[0].zipCodes
Please note, this works for the above JSON as there is only 1 country in countries array and same as for states and cities. However, if there are more than 1 country, state or city then, you will have to iterate to extract information until and unless you know the exact index.

As this is not an associative array, your option is only to use indexes like this:
countries[x].states[y].cities[0].zipCodes
Where x would be each representation of state in your array, in case, of course, that you have more than one.
Similarly y would be each state in each state in each country, in case you have more of those and you can do the same for cities if you need to.
EDIT:
Here's how you can iterate the array:
for(var c in countries)
{
var name = countries[c].name;
if (name === "CountryIAmLookingFor")
{
var statesList = countries[c].states;
for (var s in statesList)
{
var stateName = statesList[s].name;
.....
}
}
}
You can keep iterating until you find the country, state, and city you need, then extract the zipCodes from there as shown in the previous code snippet.

Without "looping"
You can do this crazy trick (not saying this is the best way, but this way you aren't looping through the JSON):
var myData = { 'Put Your Data': 'HERE' };
function getCodes(name, data) {
var sv = data.match(new RegExp(name+'([\\S\\s]*?}][\\S\\s]*?}])'))[1].match(/zipCodes":\[(.*?)\]/g), r = [];
sv.forEach(function (item) {
item.match(/\d+/g).forEach(function (sub) {
r.push(+sub);
});
});
return r;
}
getCodes('India', JSON.stringify(myData));
If your data is already string, then you don't need the JSON.stringify. The forEach you see isn't actually "looping" through the JSON. It's already extracted the zip codes and the code just adds the zip codes to the array. . This line:
var sv = JSON.stringify(data).match(new RegExp(name+'([\\S\\s]*?}][\\S\\s]*?}])'))[1].match(/zipCodes":\[(.*?)\]/g), r = [];
is what grabs the zip codes, it gets something like:
["zipCodes":["768019","768020"]"]
The next line:
item.match(/\d+/g)
will grab the numbers outputting something like:
["768019", "768020"]
The loop just adds the zip-codes to another array
With looping
You're better off looping through the JSON:
var myData = {}, // Your data
zips = [];
myData.countries.forEach(function(i) {
if (i.name === 'India') {
i.states.forEach(function(j) {
j.cities.forEach(function(l) {
l.zipCodes.forEach(function(m) {
zips.push(m);
});
});
});
}
});
//use "zips" array
PERFORMANCE AND SPEED TESTS
After testing copying an array about 500MB (half a gig) took about 30 seconds. That's a lot. Considering an extremely large JSON would be about ~5MB, looping through a little over 5MB of JSON takes about 0.14 seconds. You should never worry about speed.

Here's my "trick" for avoiding explicit iteration. Let JSON.parse or JSON.stringify do the work for you. If your JSON is in string form, try this:
var array = [];
JSON.parse(jsonString, function (key, value) {
if (key === "zipCodes") {
array = array.concat(value);
}
return value;
});
console.log(array); // all your zipCodes

Suppose your Json is like
countries =[
{
name:'India',
states:[{
name:'Orissa',
cities:[{
name:'Sambalpur',
zipCodes:768019768020
}]
},{
name:'mumbai',
cities:[{
name:'rea',
zipCodes:324243
}]
}]
}
]
So now we use MAP it will give you ZipCode of every cities
countries.map(function(s){
s.states.map(function(c){
c.cities.map(function(z){
console.log(z.zipCodes)
})
})
})
OR
If you use return statement then it will give you 2 array with two zip code as per over JSON
var finalOP = countries.map(function(s){
var Stalist = s.states.map(function(c){
var zip = c.cities.map(function(z){
return z.zipCodes
})
return zip
})
return Stalist
})
console.log(finalOP)

Reconstruct JSON after duplicates have been removed

I have the following JSON -
{
"node1":[
{
"one":"foo",
"two":"foo",
"three":"foo",
"four":"foo"
},
{
"one":"bar",
"two":"bar",
"three":"bar",
"four":"bar"
},
{
"one":"foo",
"two":"foo",
"three":"foo",
"four":"foo"
}
],
"node2":[
{
"link":"baz",
"link2":"baz"
},
{
"link":"baz",
"link2":"baz"
},
{
"link":"qux",
"link2":"qux"
},
]
};
I have the following javascript that will remove duplicates from the node1 section -
function groupBy(items, propertyName) {
var result = [];
$.each(items, function (index, item) {
if ($.inArray(item[propertyName], result) == -1) {
result.push(item[propertyName]);
}
});
return result;
}
groupBy(catalog.node1, 'one');
However this does not account for dupicates in node2.
The resulting JSON I require is to look like -
{
"node1":[
{
"one":"foo",
"two":"foo",
"three":"foo",
"four":"foo"
},
{
"one":"bar",
"two":"bar",
"three":"bar",
"four":"bar"
}
],
"node2":[
{
"link":"baz",
"link2":"baz"
},
{
"link":"qux",
"link2":"qux"
},
]
};
However I cannot get this to work and groupBy only returns a string with the duplicates removed not a restructured JSON?

You should probably look for some good implementation of a JavaScript set and use that to represent your node objects. The set data structure would ensure that you only keep unique items.
On the other hand, you may try to write your own dedup algorithm. This is one example
function dedup(data, equals){
if(data.length > 1){
return data.reduce(function(set, item){
var alreadyExist = set.some(function(unique){
return equals(unique, item);
});
if(!alreadyExist){
set.push(item)
}
return set;
},[]);
}
return [].concat(data);
}
Unfortunately, the performance of this algorithm is not too good, I think somewhat like O(n^2/2) since I check the set of unique items every time to verify if a given item exists. This won't be a big deal if your structure is really that small. But at any rate, this is where a hash-based or a tree-based algorithm would probably be better.
You can also see that I have abstracted away the definition of what is "equal". So you can provide that in a secondary function. Most likely the use of JSON.stringify is a bad idea because it takes time to serialize an object. If you can write your own customized algorithm to compare key by key that'd be probably better.
So, a naive (not recommended) implementation of equals could be somewhat like the proposed in the other answer:
var equals = function(left, right){
return JSON.stringify(left) === JSON.stringify(right);
};
And then you could simply do:
var res = Object.keys(source).reduce(function(res, key){
res[key] = dedup(source[key], equals);
return res;
},{});

Here is my version:
var obj = {} // JSON object provided in the post.
var result = Object.keys(obj);
var test = result.map(function(o){
obj[o] = obj[o].reduce(function(a,c){
if (!a.some(function(item){
return JSON.stringify(item) === JSON.stringify(c); })){
a.push(c);
}
return a;
},[]); return obj[o]; });
console.log(obj);//outputs the expected result
Using Array.prototype.reduce along with Array.prototype.some I searched for all the items being added into the new array generated into Array.prototype.reduce in the var named a by doing:
a.some(function(item){ return JSON.stringify(item) === JSON.stringify(c); })
Array.prototype.some will loop trough this new array and compare the existing items against the new item c using JSON.stringify.

Try this:
var duplicatedDataArray = [];
var DuplicatedArray = [];
//Avoiding Duplicate in Array Datas
var givenData = {givenDataForDuplication : givenArray};
$.each(givenData.givenDataForDuplication, function (index, value) {
if ($.inArray(value.ItemName, duplicatedDataArray) == -1) {
duplicatedDataArray.push(value.ItemName);
DuplicatedArray.push(value);
}
});