I am looking for a solution to sort an array by the sum of an array property within an object.
For example if the main array is
[
{
"Grid": {
"Day": [
11,
12
]
},
"Name": "One"
},
{
"Grid": {
"Day": [
5,
2
]
},
"Name": "Two"
}
]
How can I sort the sum of Day to return as
[
{
"Grid": {
"Day": [
5,
2
]
},
"Name": "Two"
},
{
"Grid": {
"Day": [
11,
12
]
},
"Name": "One"
}
]
You just need sort your array with comparator, that uses reduce to calc sum of inner array values:
let arr = [{"Grid": {"Day": [11,12]}, "Name": "One"},
{"Grid": {"Day": [5,2]}, "Name": "Two"},
{"Grid": {"Day": [1,2]}, "Name": "Two"}];
let sum = el => el.Grid.Day.reduce((a,b) => a + b);
arr.sort((a,b) => sum(a) - sum(b));
console.log(arr)
You can use a combination of reduce to sum the array, and sort to order the output:
var input = [
{
"Grid": {
"Day": [
11,
12
]
},
"Name": "One"
},
{
"Grid": {
"Day": [
5,
2
]
},
"Name": "Two"
}
];
var result = input.sort( (a,b) => sumOfDay(a) - sumOfDay(b));
console.log(result);
function sumOfDay(obj){
return obj.Grid.Day.reduce( (acc,curr) => acc + curr, 0);
}
Note that Array.prototype.sort actually mutates the original array in place. so the above could also do
input.sort( (a,b) => sumOfDay(a) - sumOfDay(b));
console.log(input);
So, don't fall into the trap of thinking the original array is unchanged just because I assigned the result to result!.
If you do wish to sort a copy of the array do this:
var result = input.slice().sort( (a,b) => sumOfDay(a) - sumOfDay(b));
Create a new Array of a by mapping through it and using reduce on the Day Array of Grid to get your sum which you can compare within a sort to return your list sorted by summed days.
const a = [
{
"Grid": {
"Day": [
11,
12
]
},
"Name": "One"
},
{
"Grid": {
"Day": [
5,
2
]
},
"Name": "Two"
}
]
const daySum = ({Grid}) => Grid.Day.reduce((prev, curr) => prev+curr, 0)
const sorted = [...a].sort(daySum)
console.log(sorted)
console.log(a) //Original array intact
Just "another" approach to solve the issue: assuming you (someday, later, eventually) may need to sort again, a good approach may also be to add a property to each grid item holding the sum of the days, avoiding the .reduce call every time you need to sort the array.
In this approach, .forEach is used to create the new property (through .reduce), and then .sort is used to sort the array in-place.
const input = [
{
"Grid": {
"Day": [
11,
12
]
},
"Name": "One"
},
{
"Grid": {
"Day": [
5,
2
]
},
"Name": "Two"
}
];
// Add a DaySum property evaluating the sum of the days.
input.forEach(i => i.Grid.DaySum = i.Grid.Day.reduce((a,b) => a + b));
// ^--- the second parameter (initial value) is unneeded here due to the fact that all elements are actually numeric, hence if the initial value is the first element of the array, which is a number already.
// Sor the array by that property.
input.sort((a,b) => a.Grid.DaySum - b.Grid.DaySum);
console.log(input);
Or, as suggested by #Andreas below, you can directly assign the property while sorting:
const input = [
{
"Grid": {
"Day": [
11,
12
]
},
"Name": "One"
},
{
"Grid": {
"Day": [
5,
2
]
},
"Name": "Two"
}
];
const sum = (a,b) => a + b;
input.sort((a,b) => {
a.Grid.DaySum = a.Grid.DaySum || a.Grid.Day.reduce(sum);
b.Grid.DaySum = b.Grid.DaySum || b.Grid.Day.reduce(sum);
return a.Grid.DaySum - b.Grid.DaySum;
});
console.log(input);
Related
I have a nested json array and I am trying to get the maximum value of the points attribute in this array.
data = {
"name": "KSE100",
"children": [
{
"name": "TECHNOLOGY & COMMUNICATION",
"children": [
{
"name": "TRG",
'points': -21
},
{
"name": "SYS",
},
]
},
{
"name": "OIL",
"children": [
{
"name": "PPL",
'points': 9
},
{
"name": "PSO",
'points': -19
},
]
},
]
}
I want the max value of points from under the children sections. I mean from under technology and oil sectors.
What I've done so far:
var max;
for (var i in data.children.length) {
for (var j in data.data[i]) {
var point = data.data[i].children[j]
}
}
Try the following:
data = {
"name": "KSE100",
"children": [
{
"name": "TECHNOLOGY & COMMUNICATION",
"children": [
{
"name": "TRG",
'points': -21
},
{
"name": "SYS",
},
]
},
{
"name": "OIL",
"children": [
{
"name": "PPL",
'points': 9
},
{
"name": "PSO",
'points': -19
},
]
},
]
}
var array = [];
for (var first of data.children) {
for (var second of first.children) {
if(second.points != undefined)
{
array.push(second);
}
}
}
var maximumValue = Math.max.apply(Math, array.map(function(obj) { return obj.points; }));
console.log(maximumValue);
you can use the reduce method on the array object to do this
const maxValues = []
data.children.forEach(el => {
if (el.name === 'OIL' || el.name === 'TECHNOLOGY & COMMUNICATIO'){
const max = el.children.reduce((current, previous) => {
if (current.points > previous.points) {
return current
}
}, 0)
maxValues.append({name: el.name, value: max.points})
}
})
This will give you an array of the objects with the name and max value.
First you can convert your object to a string through JSON.stringify so that you're able to use a regular expression
(?<=\"points\":)-?\\d*
To matchAll the values preceded by the pattern \"points\": that are or not negative values. After it, convert the result to a array through the spread operator ... and then reduce it to get the max value.
const data = {name:"KSE100",children:[{name:"TECHNOLOGY & COMMUNICATION",children:[{name:"TRG",points:-21},{name:"SYS"}]},{name:"OIL",children:[{name:"PPL",points:9},{name:"PSO",points:-19}]}]};
console.log(
[ ...JSON.stringify(data).matchAll('(?<=\"points\":)-?\\d*')]
.reduce((acc, curr) => Math.max(curr, acc))
)
I wasn't 100% sure, what your exact goal is, so I included a grouped max value and and overall max value with a slight functional approach.
Please be aware that some functionalities are not working in older browsers i.e. flatMap. This should anyways help you get started and move on.
const data = {
name: "KSE100",
children: [
{
name: "TECHNOLOGY & COMMUNICATION",
children: [
{
name: "TRG",
points: -21,
},
{
name: "SYS",
},
],
},
{
name: "OIL",
children: [
{
name: "PPL",
points: 9,
},
{
name: "PSO",
points: -19,
},
],
},
],
};
const maxPointsByGroup = data.children.reduce(
(acc, entry) => [
...acc,
{
name: entry.name,
max: Math.max(
...entry.children
.map((entry) => entry.points)
.filter((entry) => typeof entry === "number")
),
},
],
[]
);
console.log("grouped max:", maxPointsByGroup);
const overallMax = Math.max(
...data.children
.flatMap((entry) => entry.children.flatMap((entry) => entry.points))
.filter((entry) => typeof entry === "number")
);
console.log("overall max:", overallMax);
I can't set up an algo that counts my occurrences while respecting ESlint's 6 standards in javascript.
My input table is :
[
{
"id": 2,
"name": "Health",
"color": "0190fe"
},
{
"id": 3,
"name": "Agriculture",
"color": "0190fe"
},
{
"id": 1,
"name": "Urban planning",
"color": "0190fe"
},
{
"id": 1,
"name": "Urban planning",
"color": "0190fe"
}
]
And i want to get :
{"Urban planning": 2, "Health": 1, ...}
But that does not work with ESLINT / REACT compilation...
This is my code :
const jsonToIterate = *'MyPreviousInputJson'*
const names = []
jsonToIterate.map(item => (names.push(item.name)))
const count = []
names.forEach(item => {
if (count[item]){
count.push({text: item, value: 1})
} else {
count.forEach(function(top){top.text === item ? top.value =+ 1 : null})
}
})
Thank you so much
Well, you want an object in the end, not an array, so count should be {}. I also wouldn't use map if you're not actually returning anything from the call. You can use reduce for this:
let counts = topicsSort.reduce((p, c, i, a) => {
if (!p.hasOwnProperty(c.name)) p[c.name] = 0;
p[c.name]++;
return p;
}, {});
I'm half exppecting someone to close this as a duplicate because all you've asked for is a frequency counter. But here's an answer anyway:
const jsonToIterate = *'MyPreviousInputJson'*;
const names = {};
jsonToIterate.map(obj => {
if(obj.name in names){
names[obj.name]++
}
else{
names[obj.name] = 1;
}
})
I'm trying add a new value inside my array by id. I'm not trying add a new item in my array... For this I can use push(), but it add new item not a new value.
I'm trying do it:
My array:
const data =
[
{
"id": 1,
"year":2019,
"value": 2,
},
{
"id": 2,
"year": 2019,
"value": 89,
},
{
"id": 3,
"year": 2019,
"value": 99,
}
]
Inside an especific id I would to add a new value like this:
data.forEach(item => {
if(item.id === 2){
//data inside id 2 -> item: 55
}
})
So my new dataarray looks like this:
const data =
[
{
"id": 1,
"year":2019,
"value": 2,
},
{
"id": 2,
"year": 2019,
"value": 89,
"item": 55
},
{
"id": 3,
"year": 2019,
"value": 99,
}
]
In most of my searches, I found just how to add a new element. But this I know how to do (push()).
So how to add a new value inside specified id?
Just assign the property you want to add:
data.forEach(item => {
if(item.id === 2){
item.item = 55;
}
})
If the IDs are unique, you can use the .find() method:
var el = data.find(item => item.id === 2);
if (el) {
el.item = 55;
}
try
data.find(x=> x.id==2).item=55;
const data =
[
{
"id": 1,
"year":2019,
"value": 2,
},
{
"id": 2,
"year": 2019,
"value": 89,
},
{
"id": 3,
"year": 2019,
"value": 99,
}
]
data.find(x=>x.id==2).item=55;
console.log(data);
You can iterate and assign value based on your criteria
data.map(function(x){
if(x.id == 2){
x.value = 100;
}
})
You can implement method using Array.find to avoid unnecessary iterations:
const array = [
{
"id": 1,
"year":2019,
"value": 2,
},
{
"id": 2,
"year": 2019,
"value": 89,
},
{
"id": 3,
"year": 2019,
"value": 99,
}
];
const changeValue = (array, id, field, value) =>
array.find(el => el.id === id)[field] = value;
changeValue(array, 1, 'year', 9999);
console.log('result: ', array);
You have an array of objects and you want to add a field to one of the objects. So, first, you have to find the object you want to change. Array items can be accessed by index, but you don't know the index. There are several methods to find an item in an array.
var item = data.find(function(d, i){
return item.id === 2; //criteria
});
or in ES6 syntax:
var item = data.find(d=>d.id == 2);
after that, you can change item the way you want.
item.anotherField = 'another value';
As you said, push() adds an item to the array. It doesn't change existing items in the array.
Your code is more or less right there. To set the property of an item, you can do either object.propertyName = ... or object["propertyName"] = ....
With that, you'd simply need to update your example to look like this:
data.forEach(item => {
if(item.id === 2){
item.item = 55; //data inside id 2 -> item: 55
}
})
As a more efficient alternative, consider Array.find(). It won't continue to loop through the array after it finds the id, whereas your forEach will always loop through the array in its entirety.
const data = [ { "id": 1, "year":2019, "value": 2, }, { "id": 2, "year": 2019, "value": 89, }, { "id": 3, "year": 2019, "value": 99, } ];
( data.find(({id})=> id === 2) || {} ).item = 55;
console.log(data);
You'll notice I've followed the .find() with || {}. This is simply so that if an item with id === 2 isn't found, attempting to set the property won't throw an error.
I want to write to the array the value of each sum of all the reports.
month: donate_report.report[0].reports[0].sum
Unfortunately, this function returns an empty array:
month: donate_report.report[0].reports;
const doubles = month.map(function (elem) {
return elem.sum;
});
Could you please tell me what am I doing wrong? thanks in advance
"reports": [
{
"id": 1,
"sum": 5221,
},
{
"id": 2,
"sum": 5421,
}
]
The data structure you provided was not complete or wrong. Considering it as a object you can use map and return the sum property
var a={"reports": [
{
"id": 1,
"sum": 5221,
},
{
"id": 2,
"sum": 5421,
}
]}
const doubles=a.reports.map((e)=>e.sum);
console.log(doubles)
By using underscoreJS lib and manipulating some datas, i have this object
var data = {
"2017-09-26": [
{
"id": 274281,
"value": 10
},
{
"id": 274282,
"value": 20
}],
"2017-09-27": [
{
"id": 274281,
"value": 12
},
{
"id": 274282,
"value": 13
}],
}
i would like to obtain this result below by passing the keys as date in the child object and transform the value of id key as the new key of the value of value
var data = [{
date:"2017-09-26",
274281: 10,
274282: 20
},
{
date:"2017-09-27",
274281: 12,
274282: 13
}]
Please does someone as an idea to help me to do this and ideally efficiently?
Thanks
Here it is in one line:
Object.keys(data).map(key => ({date: key, ...data[key].reduce((p, c) => {p[c.id] = c.value; return p}, {})}))
Result:
[{
"274281":10,
"274282":20,
"date":"2017-09-26"
},
{
"274281":12,
"274282":13,
"date":"2017-09-27"
}]
You need nested loops. The first level creates the objects with the date property, then you loop over the objects in that value, and add the id: value properties to the result.
var newdata = _.map(data, (date, objects) => {
res = {date: date};
_.each(objects, obj => {
res[obj.id] = obj.value;
});
return res;
});
You can use Array.from() on the result of Object.entries(data) to create an array of objects by passing a callback function as the second argument.
Then for each sub-array, use .reduce() to create a new object from its members.
var data = {
"2017-09-26": [
{ "id": 274281, "value": 10 },
{ "id": 274282, "value": 20 }
],
"2017-09-27": [
{ "id": 274281, "value": 12 },
{ "id": 274282, "value": 13 }
],
};
const result = Array.from(Object.entries(data), ([key, arr]) =>
arr.reduce((res, {id, value}) =>
Object.assign(res, {[id]: value})
, {date: key})
);
console.log(result);
Here's one that's just about the same, but uses the new object literal spread syntax.
var data = {
"2017-09-26": [
{ "id": 274281, "value": 10 },
{ "id": 274282, "value": 20 }
],
"2017-09-27": [
{ "id": 274281, "value": 12 },
{ "id": 274282, "value": 13 }
],
};
const result = Array.from(Object.entries(data), ([key, arr]) =>
({date: key,
...Object.assign({}, ...arr.map(({id, value}) => ({[id]: value})))
})
);
console.log(result);