Develop Reference

How to return max number arr with the length of subArr?

Products Array has an array property called subArr and my goal is to return an array with the length of subArr which will include biggest numbers.
Array
const products = [
{
name: "car",
subArr: ["4", "200", "599.4", "4444"]
},
{
name: "tv",
subArr: ["44477", "50", "579.2", "3232"]
},
{
name: "glass",
subArr: ["2121.1", "6347", "8867", "90.01"]
}
];
My desired array is [44477, 4444, 8867, 6347]
I tried to map through the main array and the loop through the second one but can't figure out how to get an array with the length of subArr
const products = [
{
name: "car",
numArr: ["4", "200", "599.4", "4444"]
},
{
name: "tv",
numArr: ["44477", "50", "579.2", "3232"]
},
{
name: "glass",
numArr: ["2121.1", "6343", "8867", "90.01"]
}
];
function getMaxFromArr(products) {
if (!products.length) {
return [];
}
return products[0].numArr.map((val, index) => {
return products.map((prod) => parse(prod.numArr[index]));
});
}
const parse = value => parseFloat(value);
const result = getMaxFromArr(products);
console.log("result", result);
Any help will be appreciated

Approach:
First merge the all subArrs by reduce()
Convert them to numbers using .map(Number)
Sort the newArray and finally slice() them.
const products = [ { name: "car", subArr: ["4", "200", "599.4", "4444"] }, { name: "tv", subArr: ["44477", "50", "579.2", "3232"] }, { name: "glass", subArr: ["2121.1", "6347", "8867", "90.01"] } ];
const sortNum = (a, b) => b - a; //descending order
const findMaxArr = (arr, sArrSize) => products.reduce((a, {subArr}) => [...a, ...subArr.map(Number)],[]).sort(sortNum).slice(0, sArrSize);
console.log(findMaxArr(products, products[0].subArr.length));

Judging by your current code you're trying to "zip" the arrays within your products, but for each "column"/index that you zip, you want to grab the max value. That could be achieved by taking the max of your inner array with Math.max() and spreading (...) the mapped numbers into that. You can remove the parse() method as Math.max() will parse the strings to numbers internally.
See your modified code below (I've also modified it to use optional chaining (?.) and the nullish coalescing (??), but you can keep it to use the same if-statement you had if you wish):
const products = [ { name: "car", subArr: ["4", "200", "599.4", "4444"] }, { name: "tv", subArr: ["44477", "50", "579.2", "3232"] }, { name: "glass", subArr: ["2121.1", "6347", "8867", "90.01"] } ];
function getMaxFromArr(products) {
return products[0]?.subArr.map((val, index) =>
Math.max(...products.map((prod) => prod.subArr[index]))
) ?? [];
}
const result = getMaxFromArr(products);
console.log("result", result);

Get all the numbers to a single array using flatMap and convert them to numbers using Number
sort the array of numbers in descending order
take the top n items using slice
const products = [{name:"car",numArr:["4","200","599.4","4444"]},{name:"tv",numArr:["44477","50","579.2","3232"]},{name:"glass",numArr:["2121.1","6343","8867","90.01"]}],
topN = products
.flatMap(p => p.numArr.map(Number))
.sort((a, b) => b - a)
.slice(0, products[0].numArr.length)
console.log(topN)

const products = [{
name: "car",
numArr: ["4", "200", "599.4", "4444"]
},
{
name: "tv",
numArr: ["44477", "50", "579.2", "3232"]
},
{
name: "glass",
numArr: ["2121.1", "6343", "8867", "90.01"]
}
];
function getMaxFromArr(products) {
var BiggestNum = 0;
var BiggestNumArray = [];
if (!products.length) {
return [];
}
products.map((value, index) => {
var Array = value.numArr;
for (let i = 0; i < Array.length; i++) {
if (BiggestNum < Number(Array[i])) {
BiggestNum = Number(Array[i])
BiggestNumArray = Array
}
}
})
return BiggestNumArray
}
const parse = value => parseFloat(value);
const result = getMaxFromArr(products);
console.log("result", result);

I tried not to modify to much your code. You can read the logic in the comments:
Get the length of first numArr
Convert all strings in all numArr props to numbers and save them in a new array
Sort and slice
const products = [
{
name: "car",
numArr: ["4", "200", "599.4", "4444"]
},
{
name: "tv",
numArr: ["44477", "50", "579.2", "3232"]
},
{
name: "glass",
numArr: ["2121.1", "6343", "8867", "90.01"]
}
];
function getMaxFromArr(products) {
let allNumbers = []
if (!products.length) {
return []
}
else{
// get the length of first numArr
let subArrLength = products[0].numArr.length
// convert all strings in all numArr props to numbers and save them in a new array
products.forEach((prod) => {
prod.numArr.forEach((n) => allNumbers.push(Number(n)))
})
// sort and slice
console.log(allNumbers.sort((a,b) => a - b).slice(allNumbers.length - subArrLength))
}
}
getMaxFromArr(products)

How to convert object into array in Javascript

I have the below object obj(coming as a JSON response):
var obj = {
0: {
note: 'test1',
id: 24759045,
createTimeStamp: '2022-08-01T17:05:36.750Z',
},
1: {
note: 'test2',
id: 24759045,
createTimeStamp: '2022-08-01T17:05:51.755Z',
},
note: 'test1',
id: 24759045,
createTimeStamp: '2022-08-01T17:05:36.750Z',
};
I only want the objects with numbers("0" , "1" .. so on) to be pushed in an array.
Below is what I am trying to do:
let items = [];
for (var prop in obj) {
items.push(obj[prop]);
}
console.log(items);
// expected output:
[
{
note: 'test1',
id: 24759045,
createTimeStamp: '2022-08-01T17:05:36.750Z',
},
{
note: 'test2',
id: 24759045,
createTimeStamp: '2022-08-01T17:05:51.755Z',
},
]
Any pointers would be highly appreciated.

A few things to consider here.
Are the numeric keys ordered?
Does the order matter?
Are the numeric keys an index of the item in the array?
Are there any gaps in the numeric keys?
First solution, assuming that the numeric keys are the index in the array.
const items = Object.keys(obj).reduce((acc, key) => {
const index = parseInt(key);
if (Number.isNaN(index)) {
return acc;
}
acc[index] = obj[key];
return acc;
}, []);
Second solution, assuming that order matters, but that the numeric keys are not guaranteed to be contiguous.
const items = Object.keys(obj)
.filter((key) => Number.isNaN(parseInt(key)) === false)
.sort()
.map((key) => obj[key]);
Keep in mind that Object.keys does not guarantee that the keys are ordered alpha-numerically. So if order matters, then you have to sort them.
Third solution, if order doesn't matter.
const items = Object.keys(obj)
.filter((key) => Number.isNaN(parseInt(key)) === false)
.map((key) => obj[key]);

var result = [];
var obj = {
"0": {
"note": "test1",
"id": 24759045,
"createTimeStamp": "2022-08-01T17:05:36.750Z"
},
"1": {
"note": "test2",
"id": 24759045,
"createTimeStamp": "2022-08-01T17:05:51.755Z"
},
"note": "test1",
"id": 24759045,
"createTimeStamp": "2022-08-01T17:05:36.750Z"
}
for (var i in obj)
result.push(obj[i]);
$('#result').html(JSON.stringify(result));
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<div id="result"></div>
You can achieve this by doing the following steps.
Copied your object below -->
var obj = {
"0": {
"note": "test1",
"id": 24759045,
"createTimeStamp": "2022-08-01T17:05:36.750Z"
},
"1": {
"note": "test2",
"id": 24759045,
"createTimeStamp": "2022-08-01T17:05:51.755Z"
},
"note": "test1",
"id": 24759045,
"createTimeStamp": "2022-08-01T17:05:36.750Z"
}
Created new js array -->
var result = [];
Code -->
for (var i in obj)
result.push(obj[i]);
Find the solution from link below as well --> :) :)
https://jsfiddle.net/kavinduxo/95qnpaed/

I think you'll need to get the keys of the object, filter out the non-numeric ones, then map each key to the obj[key]:
var obj={"0":{"note":"test1","id":24759045,
"createTimeStamp":"2022-08-01T17:05:36.750Z"},"1":{"note":"test2","id":24759045,
"createTimeStamp":"2022-08-01T17:05:51.755Z"},
"note":"test1","id":24759045,"createTimeStamp":"2022-08-01T17:05:36.750Z"};
console.log(
Object.keys(obj)
.filter((key) =>!Number.isNaN(parseInt(key)))
.map((key) => obj[key])
)

want to display all maximum 'levelNumber' of objects in an array

arr1 = [
{
"levelNumber": "2",
"name": "abc",
},
{
"levelNumber": "3",
"name": "abc"
},
{
"levelNumber": "3",
"name": "raks",
}
]
my result array should have objects with max levelNumber i.e 3 in this case.
it should look like:
resultArr = [
{
"levelNumber": "3",
"name": "abc"
},
{
"levelNumber": "3",
"name": "raks",
}
]
note that here levelNumber can be anything..
please help me with the generic nodejs code to get duplicate max value objects

You can first find the max level of all the objects in the array and then filter the array
arr1 = [
{
"levelNumber": "2",
"name": "abc",
},
{
"levelNumber": "3",
"name": "abc"
},
{
"levelNumber": "3",
"name": "raks",
}
]
const maxLevel = String(Math.max(...arr1.map(obj => Number(obj.levelNumber))))
const maxLevelObjects = arr1.filter(obj => obj.levelNumber === maxLevel)
console.log(maxLevelObjects);

const data = [
{
"levelNumber": "2",
"name": "abc",
},
{
"levelNumber": "3",
"name": "abc"
},
{
"levelNumber": "3",
"name": "raks",
}
];
const levelNumbers = data.map((item) => parseInt(item.levelNumber));
const maxLevelNumber = Math.max(...levelNumbers).toString();
const highestLevelItems = data.filter((item) => item.levelNumber == maxLevelNumber);
console.log(highestLevelItems);
/* output
[
{ levelNumber: '3', name: 'abc' },
{ levelNumber: '3', name: 'raks' }
]
*/
EDIT
As #nat mentioned in comment:
if I add one more object in the array, with name = 'raks & levelNumber = '4' then it should display maximum levelNumber wrt that particular name. i.e.
{ "levelNumber": "3", "name": "abc" }, { "levelNumber": "4", "name": "raks" }
To achieve this, you have to:
make a Set of names
make a separate empty array to hold final result
repeat the above process for each name and add result in the array
return complete result
const data = [
{
"levelNumber": "2",
"name": "abc",
},
{
"levelNumber": "3",
"name": "abc"
},
{
"levelNumber": "3",
"name": "raks",
},
{
"levelNumber": "4",
"name": "raks",
},
{
"levelNumber": "5",
"name": "raks",
}
];
// 1.
const names = new Set(data.map((item) => item.name)); // Set is used to get only unique items
// 2.
const result = []; // For normal JS
// const result: Array<{levelNumber: string, name: string}> = []; // For TS
// 3.
names.forEach((name) => {
/* minify data (filter items with only particular name) e.g. [{levelNumber: '2', name: 'abc'}, {levelNumber: '3', name: 'abc'}] */
const minifiedData = data.filter((item) => item.name === name);
/* same process, now for minified array */
const levelNumbers = minifiedData.map((item) => parseInt(item.levelNumber));
const maxLevelNumber = Math.max(...levelNumbers).toString();
minifiedData.forEach((item) => {
if (item.levelNumber == maxLevelNumber)
result.push(item); // push every matching item (item with highest level) in final result
});
});
// 4.
console.log(result);

const arr1 = [
{
levelNumber: '2',
name: 'abc',
},
{
levelNumber: '3',
name: 'abc',
},
{
levelNumber: '3',
name: 'raks',
},
];
const getHighLevelElements = (array) => {
if (array.length === 0) return null;
array.sort((elem1, elem2) => {
if (Number(elem1.levelNumber) < Number(elem2.levelNumber)) {
return 1;
}
if (Number(elem1.levelNumber) > Number(elem2.levelNumber)) {
return -1;
}
return 0;
});
return array.filter((elem) => elem.levelNumber === array[0].levelNumber);
};
const resultArr = getHighLevelElements([...arr1]);
console.log(resultArr);

I would first have a variable called highestLevel to store the highest level number found in the array of objects (will be used later while looping), loop through the whole array and checking every key levelNumber and storing that number IF highestLevel is lower than the value of the current object levelNumber.
After I've looped through the array and got the actual highestLevel number, I would loop through again and only get the objects that are equivalent to my variable highestLevel

You can just iterate one time over arr1 with Array.prototype.reduce()
Code:
const arr1 = [{levelNumber: '2',name: 'abc',},{levelNumber: '3',name: 'abc',},{levelNumber: '3',name: 'raks'}]
const result = arr1.reduce((a, c) => !a.length || +c.levelNumber === +a[0].levelNumber
? [...a, c]
: +c.levelNumber > +a[0].levelNumber
? [c]
: a,
[])
console.log(result)

Categorisation of objects by comparing two objects in javascript

I am trying to categorise the objects by comparing two objects say data and categories
const data = {
"1a": {
"name": "1a",
"count": 154
},
"1b": {
"name": "1b",
"count": 765
},
"1c": {
"name": "1c",
"count": 7877
},
"777": {
"name": "777",
"count": 456
}
};
const categories = {
"A_category":["A","1a", "2a"],
"B_category":["1b", "2b"],
"C_category":["1c", "2c"],
"D_category":["1d", "2d"]
};
I want to group the data based on the category object, when there is no match the group should be others and the resultant data should be like
const resultData = [
{ group: 'Others', name: '777', count: 456 },
{ group: 'A_category', name: '1a', count: 154 },
{ group: 'B_category', name: '1b', count: 765 },
{ group: 'C_category', name: '1c', count: 7877 }
]
I used the function but not able to achieve the result
const resultData = [];
function restructure(data, categories) {
Object.keys(data).map(
dataKey => {
for (let [key, value] of Object.entries(categories)) {
value.includes(dataKey) ? resultData.push({"group": key,...data[dataKey]}) : resultData.push({"group": "Others",...data[dataKey]}) ;
break;
}
}
)
}
restructure(data,categories);

You can try this as well. Iterate over your data entries and find whether the key exists in any of the categories object data and push it into the array with found category as group or push it with Others as group as shown in the below code
const data = {
"1a": {
"name": "1a",
"count": 154
},
"1b": {
"name": "1b",
"count": 765
},
"1c": {
"name": "1c",
"count": 7877
},
"777": {
"name": "777",
"count": 456
}
};
const categories = {
"A_category": ["A", "1a", "2a"],
"B_category": ["1b", "2b"],
"C_category": ["1c", "2c"],
"D_category": ["1d", "2d"]
};
const resultData = [];
Object.entries(data).map(([key, val])=>{
let group = Object.keys(categories).find(category=>categories[category].includes(key)) || 'Others'
resultData.push({
group,
...val
})
})
console.log(resultData)

Instead of for loop you need to use filter as let category = Object.entries(categories).filter(([key, value]) => value.includes(dataKey));.
If category.length > 0 then category is available else use Others.
Try it below.
const data = {
"1a": {
"name": "1a",
"count": 154
},
"1b": {
"name": "1b",
"count": 765
},
"1c": {
"name": "1c",
"count": 7877
},
"777": {
"name": "777",
"count": 456
}
};
const categories = {
"A_category": ["A", "1a", "2a"],
"B_category": ["1b", "2b"],
"C_category": ["1c", "2c"],
"D_category": ["1d", "2d"]
};
const resultData = [];
function restructure(data, categories) {
Object.keys(data).map(
dataKey => {
let category = Object.entries(categories)
.filter(([key, value]) => value.includes(dataKey));
resultData.push({
"group": category.length > 0 ? category[0][0] : "Others",
...data[dataKey]
});
})
}
restructure(data, categories);
console.log(resultData);

That's because you're breaking out of the loop regardless of whether you found the category or not. Your for loop will only execute once then breaks immediately. If the first category object matches, it is used, if not "Others" is assigned and the loop exits without checking the rest of the categories. Only break out of the loop if the lookup is successful:
for (let [key, value] of Object.entries(categories)) {
if(value.includes(dataKey)) { // if this is the category
resultData.push({ "group": key, ...data[dataKey] }); // use it ...
return; // ... and break the loop and the current iteration of forEach. The current object is handled
}
}
resultData.push({ "group": "Others", ...data[dataKey] }); // if the return statement above is never reached, that means the category was not found, assign "Others"
BTW, you can use other array methods to shorten things out like so:
function restructure(data, categories) {
return Object.keys(data).map(key => ({
"group": Object.keys(categories).find(cat => categories[cat].includes(key)) || "Others",
...data[key]
}));
}
Then use like so:
const resultData = restructure(data, categories);
My method uses find to try to find a category key that contains the name of the object, if find fails, it returns null at which point, the || "Others" part is evaluated and "Others" will be used as the group name (Does JavaScript have "Short-circuit" evaluation?).
Demo:
const data = {"777":{"name":"777","count":456},"1a":{"name":"1a","count":154},"1b":{"name":"1b","count":765},"1c":{"name":"1c","count":7877}};
const categories = {"A_category":["A","1a","2a"],"B_category":["1b","2b"],"C_category":["1c","2c"],"D_category":["1d","2d"]};
function restructure(data, categories) {
return Object.keys(data).map(key => ({
"group": Object.keys(categories).find(cat => categories[cat].includes(key)) || "Others",
...data[key]
}));
}
const resultData = restructure(data, categories);
console.log(resultData);

add repeating strings value in json array

I have JSON as
var newJSON = [{
"key": "India",
"value": "72"
}, {
"key": "India",
"value": "27"
}, {
"key": "Pakistan",
"value": "90"
}, {
"key": "Zimbamwe",
"value": "88"
}, {
"key": "India",
"value": "100"
}, {
"key": "Pakistan",
"value": "172"
}]
I want desired result as below, where the duplicate key values have their value properties added together:
[{
"key": "India",
"value": "199"
}, {
"key": "Pakistan",
"value": "262"
}, {
"key": "Zimbamwe",
"value": "88"
}]
Please help me with this

Here is the solution:
var grouped = [];
var added = [];
for(var i = 0; i < json.length; i++) {
var indexOfCountry = added.indexOf(json[i].key);
if (indexOfCountry >= 0)
{
grouped[indexOfCountry].value = (Number(grouped[indexOfCountry].value) + Number(json[i].value)).toString();
}
else {
grouped.push(json[i]);
added.push(json[i].key);
}
}
grouped array is your desired result.
Fiddle: https://jsfiddle.net/zummw9zp/

Yet another variant with reduce
var result = newJSON.reduce(function(acc, el){
var val = acc.map[el.key];
if(!val){
acc.map[el.key] = val = { key:el.key, value: parseInt(el.value) };
acc.result.push(val);
}else{
val.value += parseInt(el.value);
}
return acc;
},{map:{}, result:[]}).result;
var newJSON = [
{"key":"India","value":"72"},{"key":"India","value":"27"},
{"key":"Pakistan","value":"90"},{"key":"Zimbamwe","value":"88"},
{"key":"India","value":"100"},{"key":"Pakistan","value":"172"}
];
document.getElementById('r').innerHTML = 'newJSON: ' + JSON.stringify(newJSON);
var result = newJSON.reduce(function(acc, el){
var val = acc.map[el.key];
if(!val){
acc.map[el.key] = val = { key:el.key, value: parseInt(el.value) };
acc.result.push(val);
}else{
val.value += parseInt(el.value);
}
return acc;
},{map:{}, result:[]}).result;
document.getElementById('r').innerHTML += '<br /><br />result: ' + JSON.stringify(result);
<div id="r"></div>

This is a classic use case for reduce, which is designed to take arrays and somehow, well, "reduce" them to other things, by looping across them and transforming the result at each iteration.
return newJSON.reduce(function(result, entry) {
key = entry.key;
result[key] = result[key] || { key: key, value: 0 };
result[key].value += entry.value;
return result;
}, {});
Using Underscore
If you're OK with using a library like Underscore, you can write this as
_.mapObject(_.groupBy(newJSON, 'key'), total)
Using a narrative style where we describe
`A(B, C)`
as
Take B and do A to it usingC
and
`A(B(C))`
as
Take C and do B to it. Then take the result and do A to it
we can almost read this as English:
Take newJSON and group it by using key. Then take the result and map the object using total
_.groupBy produces an object keyed by some property and returns groups, which are arrays of all the entries falling into each group:
{
India: [ {key: "India", value: 72}, {key: "India", value: 100... ],
...
}
total calculates the total value for each group:
function total(group) { return sum(group . map(value)); }
So it converts an array of entries
[ {key: "India", value: 72}, {key: "India", value: 100}, ... ],
into 199. We use this to map the arrays of entries to total scores using _.mapObject.
Here sum can be written as
function sum(array) { return array.reduce(add); }
function add(a, b) { return a+b; }
and value is a little utility function to retrieve the value property:
function value(entry) { return entry.value; }
So the complete solution is:
function add (a, b) { return a+b; }
function sum (array) { return array.reduce(add); }
function value (entry) { return entry.value; }
function total (group) { return sum(group . map(value)); }
_.mapObject(_.groupBy(newJSON, 'key'), total)