We Keep Coding

How to chunk an array based on another array of numbers?

I have an array of data, and an array of objects:
const data = ['1', '2', '2'];
const objlist = [{name : 'dummy'} , {name: 'new'}, {name : 'news'}, {name : 'place'}, ...]; // 5 objects
I want to chunk the objects in objlist by the numbers in data so that I get the follow result:
result = [
[{name:'dummy'}],
[{name:'new'}, {name:'news'}],
[{name : 'place'}, ...]
]
As you can see, it should be of the form:
[[{obj1}], [{obj2}, {obj3}], [{obj4}, {obj5}]]

You could push sliced parts to the result.
let array = [1, 2, 2],
objlist = [{ name: 'dummy' }, { name: 'new' }, { name: 'news' }, { name: 'place' }, { name: 'place' }],
result = [],
i = 0,
j = 0;
while (j < array.length) {
result.push(objlist.slice(i, i += array[j++]));
}
console.log(result);

You can loop through your array of numbers and for each number n use .splice(0, n) to get an array chunk from your array of objects. This will modify the array in-place, allowing your next .splice() to get the next consecutive object. For each .splice() you perform, you can .push() this into a resulting array.
See example below:
function partition([...arr], chunks) {
const res = [];
for(const n of chunks)
res.push(arr.splice(0, n)); // +n to turn the string number into a number (splice will do this conversion for you but you can take care of it explicitly as well)
return res;
}
const chunkArr = ['1', '2', '2'];
const arr = [{ name : 'dummy' }, {name: 'new' }, { name : 'news'},{name : 'place'}, {name : 'foo'}];
console.log(partition(arr, chunkArr));
Above I'm using partition([...arr], chunks) which uses the destructuring assignment syntax to perform a shallow copy of your input array. This way when you modify it inside your function using .splice(), it won't change the passed-in array.

How to reformat a JSON array into another format "grouping" based on different keys

Question: How can I reformat this JSON array by "grouping" via different keys, using ReactJS?
I have a JSON array as :
[
{Product: "Shoes", Sold: 5, Bought : 0, Reversed : 2} ,
{Product: "Table", Sold: 2, Bought : 0, Reserved : 4}
]
The reason for this is the data type I'm working with, and on realizing I need to visualize this data in a different way (due to one of the graph packages I am using) I need to structure this data as:
[
{
Status: "Sold",
Shoes : 5,
Table : 2
} ,
{
Status: "Bought",
Shoes : 0,
Table : 0
} ,
{
Status: "Reserved",
Shoes : 2,
Table : 4
}
]
So I'm grouping the data into the keys other than Product, and then the keys after this are Product with the Value being the Product and it's "status".
Frankly, I am at a complete loss as to what to do, as I'm thinking the code required to generate this would be quite convoluted, so I'm very open to know if this just is too much work.

const data = [
{
Product: "Shoes",
Sold: 5,
Bought : 0,
Reserved : 2
} , {
Product: "Table",
Sold: 2,
Bought : 0,
Reserved : 4
}
];
let resultData = [];
Object.keys(data[0]).forEach((key, idx) => {
if (idx !== 0) {
let resultUnit = {
Status: key,
};
data.forEach(item => {
return resultUnit = {
...resultUnit,
[item.Product]: item[key],
}
})
resultData.push(resultUnit);
}
})
console.log(resultData);
// 0: {Status: "Sold", Shoes: 5, Table: 2}
// 1: {Status: "Bought", Shoes: 0, Table: 0}
// 2: {Status: "Reserved", Shoes: 2, Table: 4}

You can do this using the Array.reduce function. (Actually, two reduce functions).
Here's an extensible solution that allows for other statuses.
Note that I changed everything to lowercase, as is standard convention.
const items = [
{product: "Shoes", sold: 5, bought : 0, reserved : 2} ,
{product: "Table", sold: 2, bought : 0, reserved : 4}
]
//We declare the status types here.
const keys = ["sold", "bought", "reserved"];
// Just create the initial 'statuses' array.
function initAcc(keys) {
return keys.map((key) => {
return {
status: key
}
});
}
//Here we are iterating over each item, getting it to return a single accumulator array each time.
const newItems = items.reduce((acc, cur) => {
return addItemToAccumulator(acc, cur);
}, initAcc(keys));
console.log(newItems);
// This function maps of the accumulator array (ie. over each status).
function addItemToAccumulator(acc, item) {
return acc.reduce((acc, statusLine) => {
//Find the count from the existing status if it exists,
//Add the current items count for that status to it.
const itemCount = item[statusLine.status] + (statusLine[item.product] || 0);
//Return a modified status, with the new count for that product
return [
...acc,
{
...statusLine,
[item.product]: itemCount
}
];
}, []);
}

Lets just do a simple loop function and create a couple objects to clearly solve the problem here:
const data = [YOUR_INITIAL_ARRAY];
let Sold, Bought, Reserved = {};
data.forEach(({Product, Sold, Bought, Reserved})=> {
Sold[Product] = Sold;
Bought[Product] = Bought;
Reservered[Product] = Reserved;
});
let newArray = [Sold, Bought, Reserved];
I think you can see where this is going ^ I see a few others have given complete answers, but try and go for the clear understandable route so it makes sense.
All you have to do after this is set the status which i'd do off an enum and you are good

Removing Duplicates in Arrays

I am trying to pass a function that removes duplicates from an array. It should handle strings, object, integers as well. In my code so far I am showing that it will handle strings but nothing else. How can Imake this function universalto handle numbers,handle arrays,handle objects, and mixed types?
let unique = (a) => a.filter((el, i ,self) => self.indexOf(el) ===i);
In this function I hav unique() filtering to make a new array which checks the element and index in the array to check if duplicate. Any help would be appreciated.

i think the first you should do is to sort the array ( input to the function ). Sorting it makes all the array element to be ordered properly. for example if you have in an array [ 1, 3, 4, 'a', 'c', 'a'], sorting this will result to [ 1 , 3 , 4, 'a', 'a' , 'c' ], the next thing is to filter the returned array.
const unique = a => {
if ( ! Array.isArray(a) )
throw new Error(`${a} is not an array`);
let val = a.sort().filter( (value, idx, array) =>
array[++idx] != value
)
return val;
}
let array = [ 1 , 5, 3, 2, "d", "q", "b" , "d" ];
unique(array); // [1, 2, 3, 5, "b", "d", "q"]
let obj = { foo: "bar" };
let arraySize = array.length;
array[arraySize] = obj;
array[arraySize++] = "foo";
array[arraySize++] = "baz";
array[arraySize++] = obj;
unique(array); // [1, 2, 3, 5, {…}, "b", "baz", "d", "foo", "hi", "q"]
it also works for all types, but if you pass in an array literal with arrays or objects as one of its element this code will fail
unique( [ "a", 1 , 3 , "a", 3 , 3, { foo: "baz" }, { foo: "baz" } ] ); // it will not remove the duplicate of { foo: "baz" } , because they both have a different memory address
and you should also note that this code does not return the array in the same order it was passed in , this is as a result of the sort array method

Try using sets without generics. You can write a function as
Set returnUnique(Object array[]) {
Set set=new HashSet();
for (Object obj:array) {
set.add(obj);
}
return set;
}

Delete objects from array of objects

Object {Results:Array[3]}
Results:Array[3]
[0-2]
0:Object
id=1
name: "Rick"
upper:"0.67"
1:Object
id=2
name:'david'
upper:"0.46"
2:Object
id=3
name:'ashley'
upper:null
I have this array of objects as shown above. and a variable named delete_id
delete_id = 1,2
So this indicates objects with id 1 and 2. It should delete the objects in the array of objects and give the final result as follows:
Object {Results:Array[1]}
Results:Array[3]
[0]
0:Object
id=3
name:'ashley'
upper:null
Can someone let me know how to achieve this. I tried to use this below function. It only deletes the first value in variale delete_id. i.e. id with 1 is deleted. similary if we have delete_id = 2,3 then it only deletes 2. I want to delete 2 and 3 both...
function removeID(delete_id) {
tabledata = tabledata.filter(function (obj) {
return delete_id.indexOf(obj.id);
});

You can use .split() and .map() to transform your delete_id string into an array of numeric IDs. Then, you can use .filter() to do the cleanup.
var players = [
{
id: 1,
name: "Rick",
upper: "0.67"
},{
id: 2,
name: "david",
upper: "0.46"
},{
id: 3,
name: "ashley",
upper: null
}
];
var delete_id = "1,2";
var exclude = delete_id.split(',').map(Number);
players = players.filter(function(player) {
return exclude.indexOf(player.id) == -1;
});
console.log(players);

function findObj(array,value,key) {
var result = array.filter(function (obj) {
if (obj[key] === value || obj[key] == value)
return obj;
});
return result;
};
First find the object from the
array(tabledata),value=1(delete_id),key=the key in json(id)
var selectedObj=findObj(tabledata,delete_id,'id');
get index of that object in the array
var index=tabledata.indexOf(selectedObj[0]);
delete its index
tabledata.splice(index,1);

The code runs if you change the removeID code to see if the index is equal to -1
function removeID(delete_id) {
tabledata = tabledata.filter(function(obj) {
return delete_id.indexOf(obj.id)===-1; //added === -1 here
});
}
var tabledata = [{
id: 1,
name: "Rick",
upper: "0.67"
}, {
id: 2,
name: 'david',
upper: "0.46"
}, {
id: 3,
name: 'ashley',
upper: null
}];
var ids = [1,2]; //defined it as an array (not sure if you did)
removeID(ids);
console.log(tabledata);

I assume that delete_id is an integer array. In that case you can filter to exclude provided ids with code below.
It'll check if obj.id is not in delete_id, then obj will be included in a new filtered array. Also it will leave tabledata intact.
var filtered = tabledata.filter(function(obj) {
return !(obj.id in delete_id)
})

reduce is not giving right sum

My Object groupBy.Food looks like
[
Object
amount: "15.0"
category: Object
debit: true
__proto__: Object
,
Object
amount: "10.0"
category: Object
debit: true
__proto__: Object
,
Object
amount: "11.1"
category: Object
debit: true
__proto__: Object
]
All I want is sum of amount in each object. I am using Lodash reduce as
var s = _.reduce(groupBy.Food, function(s, entry){
return s + parseFloat(entry.amount);
});
When I see value of s I get
s
"[object Object]1011.1"
What is that I am not doing right here?

By default, reduce starts out with the first two items in the list, so s will be the first item in the array and entry will be the second item the first time your function is called. Give it a value to start with:
var s = _.reduce(groupBy.Food, function(s, entry) {
return s + parseFloat(entry.amount);
}, 0);
(Array’s reduce behaves the same way.)

You can also use _.sum(array) or _.sumBy(array, [iteratee=_.identity]) for summing up for both array and object. See below examples.
_.sum([4, 2, 8, 6]); // ➜ 20
var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
_.sumBy(objects, function(o) { return o.n; }); // ➜ 20
_.sumBy(objects, 'n');// ➜ 20