Develop Reference

How do I find the latest time for each date in a JSON array?

I have this array in JSON format:
var result=[
{
"index": 13,
"id": 1122,
*

The approach below:
get a unique list of only the dates from the array i.e. dd/mm/yyyy
for each date in the unique list, create a sorted array per the times for that date
return the 0th item from that sorted array for that date
Example code:
var result = [
{
"index": 13,
"id": 1122,
"price": 100,
"dateTime": "11/12/2020 1:59"
},
{
"index": 14,
"id": 1122,
"price": 300,
"dateTime": "11/12/2020 3:15"
},
{
"index": 15,
"id": 1122,
"price": 314,
"dateTime": "11/13/2020 2:20"
},
{
"index": 16,
"id": 1122,
"price": 280,
"dateTime": "11/13/2020 2:23"
}
];
// get a list of the dates in result
// nothing fancy - the date is just a key
var dates = result.map(k => k.dateTime.substr(0, 10));
// get unique dates from this array
var uniqueDates = Array.from(new Set(dates));
// for each unique date, sort the times descending
// return the first item (latest) for that date
var filtered = uniqueDates.map(ud => {
var dateItems = result.filter(d => d.dateTime.substr(0, 10) == ud);
dateItems.sort((a, b) => (new Date(b.dateTime)).getTime() - (new Date(a.dateTime)).getTime());
return dateItems[0];
});
// output
console.log(filtered);

Sorting the Array on the Date value of dateTime, write a result array with dates-only as keys, retrieve the values of the result.
The TypeError, by the way, is because you should check for i + 1 being smaller than result.length in the loop (this will be falsy for the last element within the loop. In that case new Date(result[i+1].dateTime) will throw the error).
// initialize log helper
const log = Logger();
// create an empty Object
const result = {};
// sort data ascending
const dataSorted = getData().sort((a, b) =>
new Date(a.dateTime) - new Date(b.dateTime));
// add to result with datestring as key.
// The value with the most recent date will be preserved
// because key values are unique (so equal keys are overwritten)
dataSorted.forEach(v => result[new Date(v.dateTime).toDateString()] = v);
// the values of [result] contain the most recent records per date
log(Object.values(result));
// this can also be a one liner, using a reducer method
const resultX = Object.values(
getData()
.sort( (a, b) => new Date(a.dateTime) - new Date(b.dateTime) )
.reduce( (acc, value) =>
({...acc, [new Date(value.dateTime).toDateString()]: value}), {} )
);
log(`\n**from reducer`, resultX);
function getData() {
return [{
"index": 13,
"id": 1122,
"price": 100,
"dateTime": "11/12/2020 1:59"
},
{
"index": 14,
"id": 1122,
"price": 300,
"dateTime": "11/12/2020 3:15"
},
{
"index": 15,
"id": 1122,
"price": 314,
"dateTime": "11/13/2020 2:20"
},
{
"index": 16,
"id": 1122,
"price": 280,
"dateTime": "11/13/2020 2:23"
}
];
}
function Logger() {
const report = document.querySelector("#report") ||
document.body.insertAdjacentElement(
"beforeend",
Object.assign(document.createElement("pre"), {id: "report"}));
return (...args) => args.forEach(stuff =>
report.textContent += (stuff instanceof Object
? JSON.stringify(stuff, null, 2) : stuff) + "\n");
}

You can group the data based on date like,
const groups = data.reduce((groups, currVal) => {
const date = currVal.dateTime.split(' ')[0];
if (!groups[date]) {
groups[date] = [];
}
groups[date].push(currVal);
return groups;
}, {});
-> Here we split the date and and time part using split(' ') and took the date alone separately and form a group,
const date = currVal.dateTime.split(' ')[0];
And then you can get the recent date and time using the method,
groups[item].reduce((a, b) => (a.dateTime > b.dateTime ? a : b));
Working snippet:
const data = [
{
"index": 13,
"id": 1122,
"price": 100,
"dateTime": "11/12/2020 1:59"
},
{
"index": 14,
"id": 1122,
"price": 300,
"dateTime": "11/12/2020 3:15"
},
{
"index": 15,
"id": 1122,
"price": 314,
"dateTime": "11/13/2020 2:20"
},
{
"index": 16,
"id": 1122,
"price": 280,
"dateTime": "11/13/2020 2:23"
}
];
//Group the data based on date
const groups = data.reduce((groups, currVal) => {
const date = currVal.dateTime.split(' ')[0];
if (!groups[date]) {
groups[date] = [];
}
groups[date].push(currVal);
return groups;
}, {});
//Get the recent date and time based on each group
const result = [];
Object.keys(groups).filter(item => {
const newData = groups[item].reduce((a, b) => (a.dateTime > b.dateTime ? a : b));
result.push(newData);
});
console.log(result)

How to find data in for every day of week in mongoose node js

Query
const weekGraph = await tmUserSubscriptions.aggregate([
{
$match:{$and:[{subscriptionId: mongoose.Types.ObjectId(subscriptionId)},
{createdAt:{$gte:moment().startOf('isoweek').toDate(),
$lt:moment().endOf('isoweek').toDate()}}
]}
},
{"$project":{
"_id:":1,
"createdAt":{"$dayOfWeek":"$createdAt"},
"subscriptionId":1,
}},
{"$group":{
"_id":"$createdAt",
"count":{$sum:1},
}}
])
Result i get
"data": [
{
"_id": 7,
"count": 1
},
{
"_id": 5,
"count": 2
},
{
"_id": 6,
"count": 1
}
]
expected Result
"data": [
{
"_id": 7,
"count": 1
},
{
"_id": 6,
"count": 2
},
{
"_id": 5,
"count": 1
},
{
"_id": 4,
"count": 0
},{
"_id": 3,
"count": 0
},{
"_id": 2,
"count": 0
}{
"_id": 1,
"count": 0
}
]
So here i want to achieve all data of current week day by day, in my current query if there is no data any of week day then it will not return that day, but as per my expected result i want all day of week data, if there is no data for any of week day then it will return 0, so i want all 7 days data,
here _id is represent day of week

Mongoose/MongoDB will only return the aggregate if the key exists. Otherwise, it will not return you the data (less data to transfer through the connection is always faster). Therefore, you will need to provide your own defaults if the aggregate does not have data for you.
var results = [{ _id: 1, count: 1 }] // assumed from your response
var hasResult = []
for (var result of results) {
hasResult.push(result._id)
}
for (var i = 1; i <= 7; i++) {
if (!hasResult.includes(i)) {
results.push({ _id: i, count: 0 })
}
}
console.log(results)

How to add new value inside array of object by id (not new item)

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.

Javascript JSON file filter with object as a parameter

I'm a newbie in Javascript and I'm trying to understand the destructuring approach also with object literals. So what I'm trying to do is to create a function which has two types of arguments: 1. It's a JSON data file which I want to iterate. 2. An object literal with a random value assigned. So I'm trying to iterate with this object value passed as a parameter and filter with the data from the JSON file with an if statement inside the array of objects iterator. And add to arr all the object which match.
Thanks everyone in advance.
Array of objects:
[
{ "id": 44, "hours": 100,"finished": false },
{ "id": 22, "hours": 80,"finished": false },
{ "id": 65, "hours": 34,"finished": false },
{ "id": 1098, "hours": 21,"finished": true },
{ "id": 2, "hours": 67,"finished": false },
{ "id": 765, "hours": 32,"finished": false },
{ "id": 223, "hours": 555,"finished": false },
{ "id": 986, "hours": 2,"finished": false }
]
main.js
const data = require('./example.json')
function dataFilter (items, {id: _id, hours: _hours, finished: _finished}) {
for (let i = 0; i < items.length; i++) {
let arr = [];
if (items[i].id === _id) {
arr.push(items[i])
}
else if (items[i].hours >= _hours){
arr.push(items[i])
}
else if (items[i].finished === finished){
arr.push(items[i])
}
return arr;
}
}
console.log(dataFilter(data,{ id: 65 }));
console.log(dataFilter(data,{ hours: 30 }));

You don't need destructuring, what you need is array filter.
You also forgot to set a default {} so you can access undefined keys:
https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Objets_globaux/Array/filter
const data = [
{ "id": 44, "hours": 100,"finished": false },
{ "id": 22, "hours": 80,"finished": false },
{ "id": 65, "hours": 34,"finished": false },
{ "id": 1098, "hours": 21,"finished": true },
{ "id": 2, "hours": 67,"finished": false },
{ "id": 765, "hours": 32,"finished": false },
{ "id": 223, "hours": 555,"finished": false },
{ "id": 986, "hours": 2,"finished": false },
{ "id": 1986, "hours": 30,"finished": false },
];
function dataFilter (items, {id: _id, hours: _hours, finished: _finished} = {}) {
return items.filter((item) => item.id === _id || item.hours >= _hours || item.finished === _finished);
}
document.getElementById('results').innerHTML = `
<pre>
ID: 65
${JSON.stringify(dataFilter(data,{ id: 65 }), null, 2)}
HOURS: 30
${JSON.stringify(dataFilter(data,{ hours: 30 }), null, 2)}
</pre>
`
<div id="results"></div>
Approach with multiple filters
It is also possible to use more than one filter at once:
const data = [
{ "id": 44, "hours": 100,"finished": false },
{ "id": 22, "hours": 80,"finished": false },
{ "id": 65, "hours": 34,"finished": false },
{ "id": 1098, "hours": 21,"finished": true },
{ "id": 2, "hours": 67,"finished": false },
{ "id": 765, "hours": 32,"finished": false },
{ "id": 223, "hours": 555,"finished": false },
{ "id": 986, "hours": 2,"finished": false },
{ "id": 1986, "hours": 30,"finished": false },
];
function dataFilter (items, filters = {}) {
// this will create a list of function on the fly for every `filters` you pass.
const fnList = Object.keys(filters)
.map((key) => (list) => list.filter((item) => item[key] === filters[key]));
let res = [...items];
while (cursor = fnList.shift()) {
res = cursor(res);
}
return res;
}
document.getElementById('results').innerHTML = `
<pre>
ID: 44, HOURS: 100
${JSON.stringify(dataFilter(data,{ id: 44, hours: 100 }), null, 2)}
ID: 2, HOURS: 67
${JSON.stringify(dataFilter(data,{ id: 2 }), null, 2)}
</pre>
`
<div id="results"></div>
If you want to specify the operators used for the comparaison, use a fonction as explained here: Are Variable Operators Possible?

Looks like you want to be able to filter the data by any combination of the three items in that object.
function filterFactory({id, hours, finished}) {
return function filter(item) {
let isGoodValue = false;
if (id !== undefined && item.id === id) isGoodValue = true;
// for the second and third checks we'll short-circuit if it already
// passed an earlier check
if (!isGoodValue && hours !== undefined && item.hours >= hours) isGoodValue = true;
if (!isGoodValue && finished !== undefined && item.finished === finished) isGoodValue = true;
return isGoodValue;
};
}
data.filter(filterFactory({id: 2}));
Note that we're using the native filter method on arrays. filterFactory is a factory that makes callbacks to pass to filter based on one or more of the three factors you're filtering on.

Group sum and transform json object with values in nested array

I am trying to aggregate and transform the following json :
[
{
"orderId" : "01",
"date" : "2017-01-02T06:00:00.000Z",
"items" : [
{
"itemId": 100,
"itemCost": 12,
"itemQuantity": 10
},
{
"itemId": 102,
"itemCost": 25,
"itemQuantity": 4
}
]
},
{
"orderId": "02",
"date" : "2017-01-08T06:00:00.000Z",
"items" : [
{
"itemId": 100,
"itemCost": 15,
"itemQuantity": 2
},
{
"itemId": 101,
"itemCost": 20,
"itemQuantity": 5
},
{
"itemId": 102,
"itemCost": 25,
"itemQuantity": 1
}
]
},
{
"orderId": "03",
"date" : "2017-02-08T06:00:00.000Z",
"items" : [
{
"itemId": 100,
"itemCost": 15,
"itemQuantity": 2
},
{
"itemId": 101,
"itemCost": 20,
"itemQuantity": 5
},
{
"itemId": 102,
"itemCost": 25,
"itemQuantity": 1
}
]
}]
into an object that is grouped by itemId, and then aggregated by quantity, and aggregated by total cost (item cost * item quantity for each order) by month. Example:
[
{
"itemId": 100,
"period": [
{
"month": "01/17",
"quantity": 12,
"cost": 130
}
]
},
{
"itemId": 101,
"period": [
{
"month": "01/17",
"quantity": 5,
"cost": 100
},
{
"month": "02/17",
"quantity": 5,
"cost": 100
}
]
},
{
"itemId": 102,
"period": [
{
"month": "01/17",
"quantity": 5,
"cost": 125
},
{
"month": "02/17",
"quantity": 1,
"cost": 25
}
]
}
]
I have a small indention on my desk in which I have been beating my head trying to figure how to do this using native map/reduce or lodash.

You can do like this:
var orders = [{orderId:"01",date:"2017-01-02T06:00:00.000Z",items:[{itemId:100,itemCost:12,itemQuantity:10},{itemId:102,itemCost:25,itemQuantity:4}]},{orderId:"02",date:"2017-01-08T06:00:00.000Z",items:[{itemId:100,itemCost:15,itemQuantity:2},{itemId:101,itemCost:20,itemQuantity:5},{itemId:102,itemCost:25,itemQuantity:1}]},{orderId:"03",date:"2017-02-08T06:00:00.000Z",items:[{itemId:100,itemCost:15,itemQuantity:2},{itemId:101,itemCost:20,itemQuantity:5},{itemId:102,itemCost:25,itemQuantity:1}]}];
// First, map your orders by items
var items = {};
orders.forEach(function(order) {
// set the month of each order
var month = new Date(order.date);
month = ('0' + (month.getMonth() + 1)).slice(-2) + '/' + String(month.getFullYear()).slice(-2);
// for each item in this order
order.items.forEach(function(item) {
// here we already have both keys: "id" and "month"
// then, we make sure they have an object to match
var id = item.itemId;
if (!items[id]) {
items[id] = {};
}
if (!items[id][month]) {
items[id][month] = { cost:0, quantity:0 };
}
// keep calculating the total cost
items[id][month].cost += item.itemCost * item.itemQuantity;
items[id][month].quantity += item.itemQuantity;
});
});
// Now, we format the calculated values to your required output:
var result = Object.keys(items).map(function(id) {
var obj = {
itemId: id,
period: Object.keys(items[id]).map(function(month) {
items[id][month].month = month;
return items[id][month];
}),
};
return obj;
});
console.log(result);
Hope it helps.

You could use this transformation:
const result = Object.values(myList.reduce( (acc, o) => {
const month = o.date.substr(5,2) + '/' + o.date.substr(2,2);
return o.items.reduce ( (acc, item) => {
const it = acc[item.itemId] || {
itemId: item.itemId,
period: {}
},
m = it.period[month] || {
month: month,
quantity: 0,
cost: 0
};
m.cost += item.itemCost * item.itemQuantity;
m.quantity += item.itemQuantity;
it.period[month] = m;
acc[item.itemId] = it;
return acc;
}, acc);
}, {})).map( o =>
Object.assign({}, o, { period: Object.values(o.period) })
);
const myList = [
{
"orderId" : "01",
"date" : "2017-01-02T06:00:00.000Z",
"items" : [
{
"itemId": 100,
"itemCost": 12,
"itemQuantity": 10
},
{
"itemId": 102,
"itemCost": 25,
"itemQuantity": 4
}
]
},
{
"orderId": "02",
"date" : "2017-01-08T06:00:00.000Z",
"items" : [
{
"itemId": 100,
"itemCost": 15,
"itemQuantity": 2
},
{
"itemId": 101,
"itemCost": 20,
"itemQuantity": 5
},
{
"itemId": 102,
"itemCost": 25,
"itemQuantity": 1
}
]
},
{
"orderId": "03",
"date" : "2017-02-08T06:00:00.000Z",
"items" : [
{
"itemId": 100,
"itemCost": 15,
"itemQuantity": 2
},
{
"itemId": 101,
"itemCost": 20,
"itemQuantity": 5
},
{
"itemId": 102,
"itemCost": 25,
"itemQuantity": 1
}
]
}];
const result = Object.values(myList.reduce( (acc, o) => {
const month = o.date.substr(5,2) + '/' + o.date.substr(2,2);
return o.items.reduce ( (acc, item) => {
const it = acc[item.itemId] || {
itemId: item.itemId,
period: {}
},
m = it.period[month] || {
month: month,
quantity: 0,
cost: 0
};
m.cost += item.itemCost * item.itemQuantity;
m.quantity += item.itemQuantity;
it.period[month] = m;
acc[item.itemId] = it;
return acc;
}, acc);
}, {})).map( o =>
Object.assign({}, o, { period: Object.values(o.period) })
);
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

I think the other answers out there do a pretty good job from the vanilla angle, so I wanted to take a stab at a more lodash-intensive approach since you mentioned it as a tag. This is mainly just a fun challenge, but I hope the solution is elegant enough for you to lift components from.
Before we begin, I'll be using both the vanilla lodash module and the functional programming flavor of lodash. Let fp be the functional programming module and _ be vanilla (and let orders be your original data structure). Also, as a challenge, I'll do my best to minimize vanilla JS methods and arrow funcs to maximize lodash methods and function creation methods.
First, let's get all the items in a row, paired with their order information:
const items = _.flatMap(orders, o=> _.map(o.items, i=> [i, o]));
I know I said I wanted to minimize arrow functions, but I couldn't think of any other way to get the order object to the end of the chain. Challenge yourself to rewrite the above in terms of a composition (e.g. fp.compose or _.flow) and see what happens.
I'd say now's as good a time as any to group up our pairs by the item id:
const id_to_orders = _.groupBy(items, fp.get('[0].itemId'));
Here, fp.get('[0].itemId') gives us a function which, given an array, returns the itemId of the first element (in our case, we have a list of pairs, the first element of which is the item, the second of which is the relevant order object). Therefore, id_to_orders is a map from an item's ID to a list of all the times it was ordered.
This id_to_orders map looks pretty close to the data structure we're after. At a high level, all that's left is transforming the order data for each item into the quantity and cost, grouped by month.
const result = _.mapValues(id_map, fp.flow(
// Arrange the item's orders into groups by month
fp.groupBy(month)
// We're done with the order objects, so fp.get('[0]') filters them
// out, and the second function pairs the item's cost and quantity
, fp.mapValues(fp.flow(
fp.map(fp.flow(fp.get('[0]'), i=> [i.itemCost, i.itemQuantity]))
// Sum up the cost (left) and quantity (right) for the item for the month
, fp.reduce(add_pair, [0, 0])))
// These last couple lines just transform the resulting data to look
// closer to the desired structure.
, _.toPairs
, fp.map(([month, [cost, count]])=> ({month, cost, count}))
));
And the helpers month and add_pair referenced above:
function month([item, order]){
const date = new Date(order.date)
, month = date.getMonth() + 1
, year = date.getFullYear().toString().slice(-2);
return `${month}/${year}`;
}
function add_pair(p1, p2){
return [p1[0] + p2[0], p1[1] + p2[1]];
}
Just out of curiosity (or sadism), let's see what this whole thing would look like chained together as a single pipeline:
const get_order_data = fp.flow(
fp.flatMap(o=> _.map(o.items, i=> [i, o]))
, fp.groupBy(fp.get('[0].itemId'))
, fp.mapValues(fp.flow(
fp.groupBy(month)
, fp.mapValues(fp.flow(
fp.map(fp.flow(fp.get('[0]'), i=> [i.itemCost, i.itemQuantity]))
, fp.reduce(add_pair, [0, 0])))
, _.toPairs
, fp.map(([month, [cost, count]])=> ({month, cost, count})))
));
const result = get_order_data(orders);
You'll notice this composed version has a lot more fp (as opposed to _). If you're curious why it's easier this way, I encourage you to read the lodash FP guide.
jsfiddle with everything.
Finally, if you'd like to transform the result from the code above exactly into the output format you mentioned in your post, here's what I recommend:
const formatted = _.keys(result).map(k=> ({itemId: k, periods: result[k]}));