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Calculate object property values based on user id

Got an object containing a user id for each user and prices, would like to create a new object/array for each user (no duplicates) and be able to calculate the total sum of price for each user. Tried using Object.values() with map and filter but can't get it to work properly
{
"data": {
"item1": {
"price": "20",
"user": "user1"
},
"item2": {
"price": "10",
"user": "user2"
},
"item3": {
"price": "50",
"user": "user1"
}
}
}
Output something like this:
{
"users": {
"user1": {
"totalSum": "70",
},
"user2": {
"totalSum": "10",
}
}
}
I'm thinking about using map to present the "users"-data, maybe an array would be better?

Using function reduce.
Important: The attribute price is a String, this approach uses object Number to convert that value to a numeric one.
var obj = { "data": { "item1": { "price": "20", "user": "user1" }, "item2": { "price": "10", "user": "user2" }, "item3": { "price": "50", "user": "user1" } }};
var result = Object.keys(obj.data).reduce((a, k) => {
if (a.users[obj.data[k].user]) {
a.users[obj.data[k].user].totalSum += Number(obj.data[k].price);
} else {
a.users[obj.data[k].user] = {
"totalSum": Number(obj.data[k].price)
}
}
return a;
}, {
'users': {}
});
console.log(result);
.as-console-wrapper {
max-height: 100% !important; top: 0;
}

You could leverage ```reduce, more information here
code (haven't tried this)
var data = JSON.parse(mainObj).data;
var usersWithTotalExpenditure = Object.keys(data).reduce(function(result, key) {
var currentItem = data[key];
var useName = currentItem.user;
var price = Number(currentItem.price);
if (userName in result) {
result[userName].totalSum += price;
} else {
result[userName] = {
totalSum: price
};
}
return result;
}, {});
var resultObject = {
users: usersWithTotalExpenditure
}

You can use a forEach loop. This relies on Javascripts powerful OR operator, which coerces the first half of the expression to false if the current user's price is not defined (meaning it is a user the loop hasn't encountered before)
`c is your initial object's data, output is empty object`
const c = obj.data;
var output = {};
Object.keys(c).forEach((val) => {
output[c[val]["user"]] = parseInt(output[c[val]["user"]]) + parseInt(c[val]["price"]) || parseInt(c[val]["price"]);
})

How to add a new key to multiple indices of an array of objects?

I've got an array of three people. I want to add a new key to multiple objects at once based on an array of indices. Clearly my attempt at using multiple indices doesn't work but I can't seem to find the correct approach.
var array = [
{
"name": "Tom",
},
{
"name": "Dick",
},
{
"name": "Harry",
}
];
array[0,1].title = "Manager";
array[2].title = "Staff";
console.log(array);
Which returns this:
[
{
"name": "Tom",
},
{
"name": "Dick",
"title": "Manager"
},
{
"name": "Harry",
"title": "Staff"
}
]
But I'd like it to return this.
[
{
"name": "Tom",
"title": "Manager"
},
{
"name": "Dick",
"title": "Manager"
},
{
"name": "Harry",
"title": "Staff"
}
]

You cannot use multiple keys by using any separator in arrays.
Wrong: array[x, y]
Correct: array[x] and array[y]
In your case, it will be array[0].title = array[1].title = "manager";

1st method::
array[0].title = "Manager";
array[1].title = "Manager";
array[2].title = "Staff";
array[0,1] will not work.
2nd method::
for(var i=0;i<array.length;i++) {
var msg = "Manager";
if(i===2) {
msg = "Staff"
}
array[i].title = msg
}

You can use a helper function like this
function setMultiple(array, key, indexes, value)
{
for(i in array.length)
{
if(indexes.indexOf(i)>=0){
array[i][key] = value;
}
}
}
And then
setMultiple(array, "title", [0,1], "Manager");

Try this: `
for (var i=0; var<= array.length; i++){
array[i].title = "manager";
}`
Or you can change it around so var is less than or equal to any n range of keys in the index.
EDIT: instead make var <= 1. The point is to make for loops for the range of indices you want to change the title to.

Assuming that you have a bigger set of array objects.
var array = [
{
"name": "Tom",
},
{
"name": "Dick",
},
{
"name": "Harry",
},
.
.
.
];
Create an object for the new keys you want to add like so:
let newKeys = {
'Manager': [0,2],
'Staff': [1]
}
Now you can add more such titles here with the required indexes.
with that, you can do something like:
function addCustomProperty(array, newKeys, newProp) {
for (let key in newKeys) {
array.forEach((el, index) => {
if (key.indexOf(index) > -1) { // if the array corresponding to
el[newProp] = key // the key has the current array object
} // index, then add the key to the
}) // object.
}
return array
}
let someVar = addCustomProperty(array, newKeys, 'title')

Converting a json response to my requirement

I have received a JSON response like
[
{"no":001, "location": "England", "year":"2017", "month":"4", "amount":"1000"},
{"no":002, "location": "Italy", "year":"2017", "month":"3", "amount":"8000"},
{"no":001, "location": "England", "year":"2016", "month":"2", "amount":"9000"},
{"no":001, "location": "England", "year":"2016", "month":"11","amount":"12000"}
];
I need to make it
[
{"no":001, "location": "England", "year":"2016", "amount2":"9000", "amount11":"12000"},
{"no":001, "location": "England", "year":"2017", "amount4":"1000"},
{"no":002, "location": "Italy", "year":"2017", "amount3":"8000"}
];
that is based on the no converting multiple records to one with amounts specific to months and common info ie location but same no should have different records corresponding to the year.

General advice: Collect the information by ID in another datastructure. I suppose this is an Accumulator Pattern.
var rows = [
{"no":"001","month":"4","amount":"1000"},
{"no":"002","month":"3","amount":"8000"},
{"no":"001","month":"2","amount":"9000"},
{"no":"001","month":"11","amount":"12000"}
];
var results = [];
var idToResultsObject = {};
for (var i = 0; i < rows.length; i++) {
var row = rows[i];
var id = row['no'];
if (typeof idToResultsObject[id] == 'undefined')
idToResultsObject[id] = { 'no' : id };
idToResultsObject[id]['location'] = row['location'];
idToResultsObject[id]['amount' + row['month']] = row['amount'];
}
for (var id in idToResultsObject) {
results.push(idToResultsObject[id]);
}
console.log(results);
Surely there is a nicer way to store this.

Here is updated es5 code to match your latest edit of the question:
(I'm still not sure I understand what you want from no so for now I leave it as number which it is in input (not in quotes)
var input = [
{"no":001, "location": "England", "year":"2017", "month":"4", "amount":"1000"},
{"no":002, "location": "Italy", "year":"2017", "month":"3", "amount":"8000"},
{"no":001, "location": "England", "year":"2016", "month":"2", "amount":"9000"},
{"no":001, "location": "England", "year":"2016", "month":"11","amount":"12000"}
];
/*
[
{"no":001, "location": "England", "year":"2016", "amount2":"9000", "amount11":"12000"},
{"no":001, "location": "England", "year":"2017", "amount4":"1000"},
{"no":002, "location": "Italy", "year":"2017", "amount3":"8000"}
];
*/
var output = input.reduce( function(result, cur) {
var ref = result.find( function(row) {
return row.no === cur.no && row.location === cur.location && cur.year === row.year }
);
if (ref) {
ref["amount"+cur.month] = cur.amount;
} else {
var newRow = { "no": cur.no, "location": cur.location, "year": cur.year };
newRow["amount"+cur.month] = cur.amount;
result.push(newRow);
}
return result;
},[])
console.log(output);

As others have suggested, it's really a bad way to design those objects. But this code does what you want (es6 syntax):
var input = [
{"no":001,"month":"4","amount":"1000"},
{"no":002,"month":"3","amount":"8000"},
{"no":001,"month":"2","amount":"9000"},
{"no":001,"month":"11","amount":"12000"}
];
/*
[
{"no":001, "amount2":"9000", "amount4":"1000", "amount11":"12000"},
{"no":002, "amount3":"8000"}
];
*/
var output = input.reduce( (result, cur) => {
var ref = result.find( row => row.no === cur.no);
if (ref) {
ref["amount"+cur.month] = cur.amount;
} else {
var newRow = { "no": cur.no };
newRow["amount"+cur.month] = cur.amount;
result.push(newRow);
}
return result;
},[])
console.log(output);

es5 syntax
var input = [
{"no":001,"month":"4","amount":"1000"},
{"no":002,"month":"3","amount":"8000"},
{"no":001,"month":"2","amount":"9000"},
{"no":001,"month":"11","amount":"12000"}
];
/*
[
{"no":001, "amount2":"9000", "amount4":"1000", "amount11":"12000"},
{"no":002, "amount3":"8000"}
];
*/
var output = input.reduce( function(result, cur) {
var ref = result.find( function(row) { return row.no === cur.no });
if (ref) {
ref["amount"+cur.month] = cur.amount;
} else {
var newRow = { "no": cur.no };
newRow["amount"+cur.month] = cur.amount;
result.push(newRow);
}
return result;
},[])
console.log(output);

Merging linked Data in Array in Javascript

I have a simple task of rearranging a couple of Arrays in a JSON, so ractive.js can handle it better. But I got carried away a bit, and the outcome was not particularly satisfactory.
An example of my initial Array:
[{
"_id": 1,
"type": "person",
"Name": "Hans",
"WorksFor": ["3", "4"],
}, {
"_id": 2,
"type": "person",
"Name": "Michael",
"WorksFor": ["3"],
}, {
"_id": 3,
"type": "department",
"Name": "Marketing"
}, {
"_id": 4,
"type": "department",
"Name": "Sales"
}, {
"_id": 5,
"type": "person",
"Name": "Chris",
"WorksFor": [],
}]
So with a given Department I wanted a method in ractive to give me all Persons who work in this Department (with a list of Departments they work for). Something like:
[{
"_id": 1,
"type": "person",
"Name": "Hans",
"WorksFor": ["3", "4"],
"Readable": ["Marketing", "Sales"]
}, {
"_id": 2,
"type": "person",
"Name": "Michael",
"WorksFor": ["3"],
"Readable": ["Sales"]
}]
The function that somehow came to life was similar to this:
function imsorryforthis() {
let output = [];
let tempdocs = this.get('docs'); //as this happens in a ractive method,
//"this.get" is neccesary for binding
for (var i = 0; i < tempdocs.length; i++) {
if (_.contains(tempdocs[i].WorksFor, givenDepartment)) { //I used underscore.js here
let collectedDepartmentData = [];
if (tempdocs[i].WorksFor.length > 0) {
for (var f = 0; f < tempdocs[i].WorksFor.length; f++) {
for (var g = 0; g < tempdocs.length; g++) {
if (tempdocs[i].WorksFor[f] == tempdocs[g]._id) {
let actualDepartmentData = {};
actualDepartmentData = tempdocs[g];
collectedDepartmentData.push(actualDepartmentData);
}
}
}
}
tempdocs[i].Readable = collectedDepartmentData;
output.push(tempdocs[i]);
}
}
return output;
}
I've put it in a Fiddle as well to make it better readable.
Due to the fact that somehow this monstrosity does work (I was astonished myself), it feels like scratching your left ear with your right hand over your head (while being constantly shouted at by a group of desperate mathematicians).
Maybe anybody knows a more presentable and smarter approach (or a way to compile JavaScript so this never sees the light of day again).

Construct a map department_id => department_name first:
let departments = {};
for (let x of data) {
if (x.type === 'department') {
departments[x._id] = x.Name;
}
}
Then, iterate over Persons and populate Readable arrays from that map:
for (let x of data) {
if (x.type === 'person') {
x.Readable = x.WorksFor.map(w => departments[w]);
}
}
Finally, extract Persons for the specific Department:
personsInSales = data.filter(x =>
x.type === 'person' && x.WorksFor.includes('3'));

Firstly, your data structure does not have a good design. You should not be returning person and department in the same array. If possible, try to redesign the initial data structure to make it more modular, by separating out the people and department into separate structures. However if you are stuck with this same data structure, you can write the code a little better. Please find the code below. Hope it helps!
function mapPeopleDepartment() {
var deptMap = {},peopleList = [];
//Iterate through the initialArray and separate out the department into a hashmap deptMap and people into a new peopleList
for(var i=0; i < initArray.length; i++) {
var obj = initArray[i];
obj.type == "department" ? deptMap[obj._id] = obj.Name : peopleList.push(obj);
}
//Iterate through the peopleList to map the WorksFor array to a Readable array
for(var i=0; i < peopleList.length; i++) {
var person = peopleList[i];
person.Readable = _.map(person.WorksFor, function(dept){return deptMap[dept]});
}
return peopleList;
}

Data manipulation in DataTables

I have a quite complex data manipulation to perform.
My datasource gives me a list of cashflows, grouped by person like that:
{
"months": [
"2016-10-01",
"2016-11-01",
"2016-12-01",
"2017-01-01"
],
"persons": [
{
"label": "John",
"cashflows": [
{
"date": "2016-10-01",
"amount": "1000.00"
},
{
"date": "2016-11-01",
"amount": "1000.00"
}
]
},
{
"label": "Brad",
"cashflows": [
{
"date": "2017-01-01",
"amount": "5540.00"
}
]
}
]
}
I want to put those data in a DataTable, but I don't know how to "JOIN" the months and the cashflows.
My best guest is a sql-like query, but in javascript, in order to perform this pseudo-code:
select each person
for each person
good_row = person.cashflows LEFT JOIN months ON cashflows.date (iiish..)
I have set up a jsfiddle here.

Here is the plain javascript way to do it (the hard way).
Fiddle link: https://jsfiddle.net/ngwqfjo0/
function getDesiredData() {
var persons = real_data["persons"];
var months = real_data["months"];
persons.forEach(function(person) {
var row = [];
var amounts = [];
row.push(person["label"]);
months.forEach(function(month) {
var amount = '';
for(x = 0; x < person["cashflows"].length; x++) {
if(month == person["cashflows"][x]["date"]) {
amount = person["cashflows"][x]["amount"];
break;
}
}
amounts.push(amount);
});
desiredData.push(row.concat(amounts));
});
return desiredData;
}
To make life easier, consider using a functional utility like lodash or underscore
function getDesiredDataEasy() {
var persons = real_data["persons"];
var months = real_data["months"];
var desiredData = [];
return _.map(persons, function(person) {
return _.concat([person["label"]], _.map(months, function(month) {
var cashFlowDate = _.find(person["cashflows"], function(cf) {
return cf.date == month;
});
return cashFlowDate ? cashFlowDate.amount : "";
}));
});
}