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Repeat every element in array based on object properties

I have an array that I'm retrieving from an API. The array looks like this:
[{
"name": "Rachel",
"count": 4,
"fon": "46-104104",
"id": 2
},
{
"name": "Lindsay",
"count": 2,
"fon": "43-053201",
"id": 3
},
{
"name": "Michael",
"count": 5,
"fon": "46-231223",
"id": 4
}]
Then I loop through the array to create an array containing only the names.
function buildName(data) {
for (var i = 0; i < data.length; i++) {
nameList.push(data[i].name)
}
}
This also works so far, but I would like to create an array in which each name occurs as often as the object count says.
For example, the name Michael should appear five times in the array and Lindsay twice.
[
"Rachel",
"Rachel",
"Rachel",
"Rachel",
"Lindsay",
"Lindsay",
"Michael",
"Michael",
"Michael",
"Michael"
"Michael"
]

For each object create a new array using count, and then fill it with the name.
If you use flatMap to iterate over the array of objects. It will return a new array of nested objects but then flatten them into a non-nested structure.
const data=[{name:"Rachel",count:4,fon:"46-104104",id:2},{name:"Lindsay",count:2,fon:"43-053201",id:3},{name:"Michael",count:5,fon:"46-231223",id:4}];
const out = data.flatMap(obj => {
return new Array(obj.count).fill(obj.name)
});
console.log(out);

I've upgraded your functions but you can use the map method
function buildName(data){
for (let i = 0; i < data.length; i++){
let numToLoop = data[i].count
let name = data[i].name
for (let z = 0; z < +numToLoop; z++){
nameList.push(name)
}
}
}

Use an inner while loop inside the for loop:
const data = [{
"name": "Rachel",
"count": 4,
"fon": "46-104104",
"id": 2
},
{
"name": "Lindsay",
"count": 2,
"fon": "43-053201",
"id": 3
},
{
"name": "Michael",
"count": 5,
"fon": "46-231223",
"id": 4
}]
function buildName(data){
const result = [];
for (let i = 0; i < data.length; i += 1) {
let item = data[i];
let count = item.count;
while (count > 0) {
result.push(item.name);
count -= 1;
}
}
return result;
}
console.log(buildName(data));

Just add an inner loop with as many iterations as the "count" property in the object:
function buildName(data) {
const nameList = [];
for (var i = 0; i < data.length; i++) {
for (let j = 0; j < data[i].count; j++) {
nameList.push(data[i].name);
}
}
return nameList;
}

For fun
import { pipe } from 'fp-ts/lib/function';
import { chain, replicate } from 'fp-ts/lib/Array';
const arr = ...
const result = pipe(
arr,
chain(i => replicate(i.count, i.name))
);

You can use .flapMap() for that:
const arr = [{ "name": "Rachel", "count": 4, "fon": "46-104104", "id": 2 }, { "name": "Lindsay", "count": 2, "fon": "43-053201", "id": 3 }, { "name": "Michael", "count": 5, "fon": "46-231223", "id": 4 }];
const result = arr.flatMap(({count, name}) => Array(count).fill(name));
console.log(result);
Effectively you turn every element into an array of the the name property repeated count times which is then flattened into a single array.

It can be done via creating an array with repeated names in this way:
Array(count).fill(name)
Then you have to spread it into resulting array.
You can try this one-liner
const getNames = (data) =>
data.reduce(
(names, { name, count }) => [...names, ...Array(count).fill(name)],
[]
)
Note that a pure function is presented here, which is generally the preferred way of writing code. However, updating your example code might look like this
const getNames = (data) =>
data.reduce(
(names, { name, count }) => [...names, ...Array(count).fill(name)],
[]
)
function buildName(data) {
nameList = getNames(data)
}

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')

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;
}

JSON data transformation from table-like format to JSON?

I have data that's in this format:
{
"columns": [
{
"values": [
{
"data": [
"Project Name",
"Owner",
"Creation Date",
"Completed Tasks"
]
}
]
}
],
"rows": [
{
"values": [
{
"data": [
"My Project 1",
"Franklin",
"7/1/2015",
"387"
]
}
]
},
{
"values": [
{
"data": [
"My Project 2",
"Beth",
"7/12/2015",
"402"
]
}
]
}
]
}
Is there some super short/easy way I can format it like so:
{
"projects": [
{
"projectName": "My Project 1",
"owner": "Franklin",
"creationDate": "7/1/2015",
"completedTasks": "387"
},
{
"projectName": "My Project 2",
"owner": "Beth",
"creationDate": "7/12/2015",
"completedTasks": "402"
}
]
}
I've already got the column name translation code:
r = s.replace(/\%/g, 'Perc')
.replace(/^[0-9A-Z]/g, function (x) {
return x.toLowerCase();
}).replace(/[\(\)\s]/g, '');
Before I dive into this with a bunch of forEach loops, I was wondering if there was a super quick way to transform this. I'm open to using libraries such as Underscore.

function translate(str) {
return str.replace(/\%/g, 'Perc')
.replace(/^[0-9A-Z]/g, function (x) {
return x.toLowerCase();
})
.replace(/[\(\)\s]/g, '');
}
function newFormat(obj) {
// grab the column names
var colNames = obj.columns[0].values[0].data;
// create a new temporary array
var out = [];
var rows = obj.rows;
// loop over the rows
rows.forEach(function (row) {
var record = row.values[0].data;
// create a new object, loop over the existing array elements
// and add them to the object using the column names as keys
var newRec = {};
for (var i = 0, l = record.length; i < l; i++) {
newRec[translate(colNames[i])] = record[i];
}
// push the new object to the array
out.push(newRec);
});
// return the final object
return { projects: out };
}
DEMO

There is no easy way, and this is really not that complex of an operation, even using for loops. I don't know why you would want to use regex to do this.
I would start with reading out the column values into a numerically indexed array.
So something like:
var sourceData = JSON.parse(yourJSONstring);
var columns = sourceData.columns[0].values[0].data;
Now you have a convenient way to start building your desired object. You can use the columns array created above to provide property key labels in your final object.
var sourceRows = sourceData.rows;
var finalData = {
"projects": []
};
// iterate through rows and write to object
for (i = 0; i < sourceRows.length; i++) {
var sourceRow = sourceRows[i].values.data;
// load data from row in finalData object
for (j = 0; j < sourceRow.length; j++) {
finalData.projects[i][columns[j]] = sourceRow[j];
}
}
That should do the trick for you.

Is there possible to loop inside JavaScript object literal

So this is my question (maybe stupid), is there any possible to do this:
var data {
"label" : value,
"sets" : [
for (var i=0; i < item.length; i++)
{
somedata: "data"
}
]
}
to reach result:
var data {
"label" : value,
"sets" : [
{
somedata: "data1"
},
{
somedata: "data2"
}
]
}
Much thx for help.

As jimm101 has pointed out, you are not working with JSON, that's just JavaScript (the var in there proves it) . If you want to calculate a value inside a literal JavaScript object, you can use an immediately invoked function
var data = {
"label" : value,
"sets" : (function(){
var arr = [];
for (var i=0; i < item.length; i++) {
arr.push( {somedata: "data" + i} ) ;
}
return arr;
})()
};
As dystroy has pointed out You can also use Array.map to return a transformed array, without needing an immediately invoked function, which looks a little nicer

You may use functional programming :
var data = {
"label" : "value",
"sets" : item.map(function(_,i){ return {somedata: "data"+(i+1)} })
}

Use the following:
var data = {
label: value,
get sets(){
var array = [];
/* write your logic to fill the array here. */
return array;
}
}
Reference here

As others have commented, JSON is data, not code. It looks like you're making javascript code though, since JSON also wouldn't include the var data part.
JSON => JavaScript Object Notation, a wide-spread way of representing data.
javascsript object => A structure within the javascript programming language that uses JavaScript Object Notation.
You can do something like this.
var data = {
"label" : 'my_label',
};
item = ['one','two','another'];
data.sets = [];
for (var i=0; i < item.length; i++)
{
data.sets.push({'somedata': item[i]});
}

You can use array comprehension (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Array_comprehensions), but it's not supported yet by all browsers (ECMAScript 6).
var value = "test";
var item = ["data1", "data2", "data3"];
var data = {
"label" : value,
"sets" : [for (x of item) {somedata: x}]
};
/*
Result :
data = {
"label":"test",
"sets":[
{"somedata":"data1"},
{"somedata":"data2"},
{"somedata":"data3"}
]
}
*/

You can have nested data in JSON like for example
var myObject = {
"first": "John",
"last": "Doe",
"age": 39,
"sex": "M",
"salary": 70000,
"registered": true,
"interests": [ "Reading", "Mountain Biking", "Hacking" ],
"favorites": {
"color": "Blue",
"sport": "Soccer",
"food": "Spaghetti"
},
"skills": [
{
"category": "JavaScript",
"tests": [
{ "name": "One", "score": 90 },
{ "name": "Two", "score": 96 }
]
},
{
"category": "CouchDB",
"tests": [
{ "name": "One", "score": 79 },
{ "name": "Two", "score": 84 }
]
},
{
"category": "Node.js",
"tests": [
{ "name": "One", "score": 97 },
{ "name": "Two", "score": 93 }
]
}
]
};
You can access such an array and its contents using a loop in your program
Source: http://www.json.com/