Develop Reference

Javascript grouping by data from data and returning array of objects

I have 100 objects of data within an array that looks like this:
{
id: "1",
date: "2022/01/01",
name: "John",
},
{
id: "2",
date: "2022/01/02",
name: "Chris",
},
I am trying to return an array of objects by date that also returns the names.
For example:
[
{
date: "2022/01/01",
names: ["John", "Steve"...]
},
{
date: "2022/01/02",
names: ["Chris", "Rob"...]
},
]
I have tried using the reduce method:
const groupedByDate = () =>
data.reduce((itemsIterated, { date, name }) => {
if (!itemsIterated[date]) {
itemsIterated[date] = {
date,
names: [],
};
}
itemsIterated[date].names.push(name);
return itemsIterated;
}, []);
The issue is this gives me array with a key of the date and then the object with date/names but I don't know how to return just the array of objects by date.

The function groupedByDate would return an object like this -
const result = {
'2022/01/01': {
date: "2022/01/01",
names: ["John", "Steve"...]
},
'2022/01/02': {
date: "2022/01/02",
names: ["Chris", "Rob"...]
},
}
However, to retrieve it in the format you need, you would need to make use of Object.values().
Object.values(result);
/*
[
{
date: "2022/01/01",
names: ["John", "Steve"...]
},
{
date: "2022/01/02",
names: ["Chris", "Rob"...]
},
]
*/
NOTE
To learn more about Object.values() - MDN
reduce's second parameter is the initial value of the accumulator. Here, we would need to use {} instead of [] in the groupedByDate function.

Javascript filter parent array based on child containing value

I am trying to filter the parent array products based on the selected value which should be contained as the child. For example in my case I was trying to get all the product objects as an array which contained the string "iphone". It is not working for me and I can't seem to locate my error. Please may someone help.
What I have tried:
const selected = 'iphone'
const products = [
{
id: "4irnflpd0",
productItem: [ "iphone", "ipad", "kindle"],
},
{
id: "glrscb1m3s9k",
productItem: ["airpods","iphone",],
},
{
id: "uumkugk3jxof",
productItem: ["macbook","cable"]
},
]
var filtered = products.map(o=>{
o = Object.assign({},o); //Clone the object. So any changes will not affect the original array.
o.productItem.map(p=>{ //Use map to loop thru the products
p = p.filter(v=>v === selected); //Filter the products which include selected
});
return o;
})
Expected array output:
const products = [
{
id: "4irnflpd0",
productItem: [ "iphone", "ipad", "kindle"],
},
{
id: "glrscb1m3s9k",
productItem: ["airpods","iphone",],
},
]

Just a simple filter() method should work for us in this case. T further simplify, we can also use object restructuring, so instead of writing product.productItem.includes(selected), we'll only need to write productItem.includes(selected).
All we have to do is filter the source array by which items include the selected value:
const selected = 'iphone';
const products = [
{ id: "4irnflpd0", productItem: ["iphone", "ipad", "kindle"] },
{ id: "glrscb1m3s9k", productItem: ["airpods", "iphone", ] },
{ id: "uumkugk3jxof", productItem: ["macbook", "cable"] },
];
const filtered = products.filter(({productItem}) => productItem.includes(selected));
console.log(filtered);
If you'd prefer not to use Object destructuring, just swap that filter line for this more traditional one:
products.filter(p => p.productItem.includes(selected))
If you're not sure that every single item in your array will have the productItem key, then you should use optional chaining to prevent an error being thrown. This is as simple as adding ? before after property name. Here it is all put together:
products.filter(p => p.productItem?.includes(selected))

First of all no need to make a copy since with map function you allocated the result to new variable without changing the new array
So you need to do this
const filtered = products.map(p=>{
return p.productItem.includes(selected)
})

You can use the filter() methods on products array and find if the selected item is available in the productItems
const selected = 'iphone'
const products = [
{ id: "4irnflpd0", productItem: [ "iphone", "ipad", "kindle"] },
{ id: "glrscb1m3s9k", productItem: ["airpods","iPhone",] },
{id: "uumkugk3jxof", productItem: ["macbook","cable"] }
]
var filtered = products.filter(product =>
product.productItem?.includes(selected));
console.log(filtered);

Filtering array of objects against another array of objects?

customerProducts: [
{
name: "foo",
id: 123
},
{
name: "test",
id: 44
}
]
otherProducts: [
{
name: "other",
id: 44
},
{
name: "test",
id: 21
}
]
I want to iterate through customerProducts, which is an array of objects. I want to filter the customerProducts that have an ID that another array of objects, otherProducts, has. So for examople, I'd want the returned result in this case to be:
{
name: "test",
id: 44
}
since otherProducts has an id of 44.
I was thinking of mapping through otherProducts and just returning an array of IDs, then running a forEach on that but that seems like a long way of doing it.

Create an indexed Set of the values to filter by (id from otherProducts) then filter customerProducts by that Set
const customerProducts = [{name: "foo",id: 123},{name: "test",id: 44}]
const otherProducts = [{name: "other",id: 44},{name: "test",id: 21}]
const otherProductIds = new Set(otherProducts.map(({ id }) => id))
const filteredCustomerProducts = customerProducts.filter(({ id }) =>
otherProductIds.has(id))
console.info(filteredCustomerProducts)

This can be done by using array methods filter and some.
customerProducts.filter((x)=> otherProducts.some(y=> y.id === x.id));
Explanation:
filter method will call each and every element in the otherProducts array and check if the id of customerProduct is present in otherProducts for at least one element.

declare customerProducts , otherProducts as JS array variable and use JS Array filter find functions
let customerProducts = [
{
name: "foo",
id: 123
},
{
name: "test",
id: 44
}
]
let otherProducts = [
{
name: "other",
id: 44
},
{
name: "test",
id: 21
}
];
let filtered = customerProducts.filter( el => otherProducts.find( e => e.id == el.id) )
console.log(filtered);

how to loop through multiple arrays inside an array and filter a value from it-Javascript

I'm using EXTJS framework for my code.
below is my array structure:
data = [{
id: 22,
rows: [{
id: "673627",
name: "ABS",
address: "536street"
}, {
id: "333",
name: "TEST$$",
address: "536street"
}, {
id: "999",
name: "TEST$$",
address: "536street"
}]
}, {
id: 33,
rows: [{
id: "899",
name: "TES",
address: "536street"
}, {
id: "333",
name: "TEST$$",
address: "536street"
}, {
id: "999",
name: "TES673",
address: "536street"
}]
}]
Now I want to filter the name from this array, whose value I'm comparing with say "TEST$$".
I'm doing this;
Ext.each(data, function(item) {
filter = item.rows.filter(function(name) {
return name.name === "TEST$$";
}, this);
}, this);
console.log(filter);
In this case, it returns only 1 match, where as I have 3 matches for this particular value. It returns the match from the last item in the data array and hence I dont get all the matching values, any idea how this can be looped to get all values matching?
thx!

You're reassigning the filter variable on every iteration over the data array:
filter = item.rows.filter(function(name) {
return name.name === "TEST$$";
}, this);
On the last iteration, there is only one match, the one with id of 333, so that's the only one that you see after running the Ext.each. Try pushing to an external array that doesn't get overwritten instead:
const testItems = [];
Ext.each(data, function(item) {
const filtered = item.rows.filter(row => row.name === "TEST$$")
testItems.push(...filtered);
});
console.log(testItems);
Note that there's no need to pass along the this context.
Another option is to flatMap to extract all rows to a single array first:
const output = data
.flatMap(({ rows }) => rows)
.filter(({ name }) => name === 'TEST$$');

How to create a json grouped by date in js?

I have an array of objects sorted by date:
const alerts = [{
id: 1, date: '2018-10-31T23:18:31.000Z', name: 'Joke', title: 'this is the first 1'
}, {
id: 2, date: '2018-10-30T23:18:31.000Z', name: 'Mark', title: 'this is the second one'
}]
I am trying to 'group' the alerts by date so trying to create 'datesections' which have a dateheader, the result should be something like:
const sections = [{
date: '2018-10-31T23:18:31.000Z',
heading: 'today',
alerts: [{ id: 1, date: '2018-10-31T23:18:31.000Z', name: 'Joke',
title: 'this is the first one' }]
}, {
date: '2018-10-30T23:18:31.000Z',
heading: 'Yesterday',
alerts: [{ id: 2, date: '2018-05-30T23:18:31.000Z', name: 'Mark',
title: 'this is the second one' }]
}]
I tried something this but can't figure out how to get the alerts with the same date in the alerts prop:
const sections2=alerts.map(a =>
({
date: a.date,
heading:'today new',
alerts:alerts
})
)

const alerts = [
{ id: 1, date: '2018-10-31T23:18:31.000Z', name: 'Joke', title: 'this is the first 1' },
{ id: 2, date: '2018-05-30T23:18:31.000Z', name: 'Mark', title: 'this is the second one' }
]
const grouping = _.groupBy(alerts, element => element.date.substring(0, 10))
const sections = _.map(grouping, (items, date) => ({
date: date,
alerts: items
}));
console.log(sections);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>
Can't help you with headings - what if it's neither "today" or "yesterday"?

I feel like you are asking a couple of things here. The key one is how to group by day with a date.
To do that you will first need to know how to group. This answer may help with that.
As far as how to group by day there are a number of ways to do that. Simplest I can think of is to cut off everything after the "T" in the date string and sort that.

From my point of view it's not really a map what you need here, map will return a new array but not what you want. You can do this with 2 for statements
let total = [];
for (let j = 0; j < alerts.length; j++) {
let item = alerts[j];
let foundDate = false;
for (let i = 0; i < total.length; i++) {
if (total[i].date === item.date) {
foundDate = true;
total.alerts.push(item);
}
}
if (!foundDate) {
console.log("!found");
total.push({
date: item.date,
heading: "Yesterday",
alerts: [item]
});
}
}
If you console.log yout total array, will contain what you want.
If you need any other explanation pls let me know.

You can use a regular expression to match the part of the date you want and then group your data. You can add there the header you want. Hope this helps.
const alerts = [
{ id: 1, date: '2018-10-31T23:18:31.000Z', name: 'Joke', title: 'this is the first 1' },
{ id: 2, date: '2018-10-30T23:18:31.000Z', name: 'Mark', title: 'this is the second one' },
{ id: 3, date: '2018-10-30T23:14:32.000Z', name: 'Mark', title: 'this is the third one' }
];
const groupByDate = (data) => {
return data.reduce((acc, val) => {
const date = val.date.match(/\d{4}-\d{2}-\d{2}/g).toString();
const item = acc.find((item) => item.date.match(new RegExp(date, 'g')));
if (!item) acc.push({ date: val.date, alerts: [val], heading: 'some heading' });
else item.alerts.push(val);
return acc;
}, []);
};
console.log(groupByDate(alerts));

Maybe you need something like this? Didn't have much time for this and last array parsing might be done in more elegant way ;)
var alerts = [
{ id: 1, date: '2018-10-31T23:18:31.000Z', name: 'Joke', title: 'this is the first 1' },
{ id: 3, date: '2018-10-31T23:44:31.000Z', name: 'Joke1', title: 'this is the 2nd' },
{ id: 2, date: '2018-10-30T23:18:31.000Z', name: 'Mark', title: 'this is the second one' },
{ id: 4, date: '2018-10-30T23:45:31.000Z', name: 'Mark1', title: 'this is the 3rd' },
{ id: 5, date: '2018-10-27T23:18:31.000Z', name: 'Mark2', title: 'this is the 4th' },
];
var processedAlerts = [], finalAlerts;
(function(initAlerts){
//iterate through array to make keys to group by day
for(var i = 0; i < initAlerts.length; i++){
processedAlerts[i] = initAlerts[i];
//substring here can be more sophisticated - this was faster
initAlerts[i].keyDate = initAlerts[i].date.substr(0, 10);
}
//supporting function to convert string to date
//to acheve more detailed sorting that includes time
//just use date object and use hours, minutes and/or seconds to create Date object
function dateFromString(strDate){
var date, tmpDate;
//convert string to array - I assume that date format is always the same
//yyyy-mm-dd and will become Array 0: year, 1: month, 2: day of the month
tmpDate = strDate.split("-");
//moths in js are zero pased so Jan is 0, Feb is 1 and so on
//so we want to substract 1 from human readable month value to get correct date
date = new Date(tmpDate[0], tmpDate[1]-1, tmpDate[2]);
return date;
}
//function used to compare dates and passed to sort function
function comparedates(obj1, obj2){
var date1, date2;
date1 = dateFromString(obj1.keyDate);
date2 = dateFromString(obj2.keyDate);
let comparison = 0;
if(date1>date2){
comparison = 1;
} else if(date1<date2){
comparison = -1;
}
//to achieve reverse just multiply comparison result by -1
return comparison*(-1);
}
function getHeader(date){
//here place logic to generate header
//this involves comparing dates probably from keyDate
return "temp header: " + date.toString()
}
//sort the array by keyDate from newest to oldest
processedAlerts.sort(comparedates);
//final array rebuild
//pass here sorted array
finalAlerts = (function(arrayAlerts){
var aAlerts = [], k = 0;
for(var j = 0; j < arrayAlerts.length; j++){
//check if entry for date exists
//if no than create it
if(!aAlerts[k]){
aAlerts[k] = {
//removed title because I asummed that each alert has unique title and put them in alerts instead
date: arrayAlerts[j].keyDate, //agroupped date
heading: getHeader(arrayAlerts[j].keyDate), //update this function to return personalized heading
//here you can shape the alert object how you need
//I just passed it as it was
alerts: [arrayAlerts[j]] //array with first object inside
};
} else {
//add another alert to day
aAlerts[k].alerts.push(arrayAlerts[j]) //array with first object inside
}
//increasing final array key
//if there is previous entry and keys are the same for current and previous
if(arrayAlerts[j-1] && (arrayAlerts[j].keyDate == arrayAlerts[j-1].keyDate)){
k++;
}
}
return aAlerts;
})(processedAlerts);
})(alerts);
console.log(finalAlerts);