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JavaScript array of dates to array of ranges of dates

I have a JavaScript array of dates (as strings) like the following:
["2020-07-24T04:00:00.000Z", "2020-07-25T04:00:00.000Z", "2020-07-26T04:00:00.000Z", "2020-07-27T04:00:00.000Z", "2020-07-28T04:00:00.000Z", "2020-07-29T04:00:00.000Z", "2020-07-30T04:00:00.000Z", "2020-07-31T04:00:00.000Z", "2020-08-01T04:00:00.000Z", "2020-11-29T05:00:00.000Z", "2020-12-30T05:00:00.000Z", "2020-12-31T05:00:00.000Z", "2021-01-01T05:00:00.000Z", "2021-01-02T05:00:00.000Z", "2021-02-18T05:00:00.000Z"]
I want to convert this into an array of arrays of [first, last] contiguous date ranges, e.g., as below:
[["2020-07-24T04:00:00.000Z", "2020-08-01T04:00:00.000Z"], ["2020-11-29T05:00:00.000Z"], ["2020-12-30T05:00:00.000Z", "2021-01-02T05:00:00.000Z"], []]
How do I do this? Code attempt below:
var ranges = [];
for (var i = 0; i < popNull.length; i++) {
let currentRange = [];
let current = new Date(popNull[i]);
let tomorrow = new Date(current.getTime() + (24 * 60 * 60 * 1000));
let next = new Date(popNull[i+1]);
if (next === tomorrow) {
}
else {
}
}

I've made a couple of assumptions in the code below
That the dates are pre-sorted in ascending date order
That "contiguous" means less than or equal to 24 hours.
All dates are formatted in a way that can be passed directly to the Date constructor on the platform of choice.
const input = ["2020-07-24T04:00:00.000Z", "2020-07-25T04:00:00.000Z", "2020-07-26T04:00:00.000Z", "2020-07-27T04:00:00.000Z", "2020-07-28T04:00:00.000Z", "2020-07-29T04:00:00.000Z", "2020-07-30T04:00:00.000Z", "2020-07-31T04:00:00.000Z", "2020-08-01T04:00:00.000Z", "2020-11-29T05:00:00.000Z", "2020-12-30T05:00:00.000Z", "2020-12-31T05:00:00.000Z", "2021-01-01T05:00:00.000Z", "2021-01-02T05:00:00.000Z", "2021-02-18T05:00:00.000Z"].map(x => new Date(x));
let aggregation = input.reduce( (acc,i) => {
if(acc.prev){
const diffInHrs = (i - acc.prev)/1000/60/60;
if(diffInHrs <= 24){
acc.result[acc.result.length-1][1] = i;
}
else{
acc.result.push([i])
}
acc.prev = i;
return acc;
}
else{
return {prev:i, result:[[i]]}
}
},{});
console.log(aggregation.result)

You can reduce the dates by keeoing track of the latest and checking the current with the previous. You can diff their epoch valyes and check if they are within a day.
const dates = ["2020-07-24T04:00:00.000Z", "2020-07-25T04:00:00.000Z", "2020-07-26T04:00:00.000Z", "2020-07-27T04:00:00.000Z", "2020-07-28T04:00:00.000Z", "2020-07-29T04:00:00.000Z", "2020-07-30T04:00:00.000Z", "2020-07-31T04:00:00.000Z", "2020-08-01T04:00:00.000Z", "2020-11-29T05:00:00.000Z", "2020-12-30T05:00:00.000Z", "2020-12-31T05:00:00.000Z", "2021-01-01T05:00:00.000Z", "2021-01-02T05:00:00.000Z", "2021-02-18T05:00:00.000Z"];
const DAY_MILLIS = 8.64e7;
const ranges = dates
.reduce((acc, dateStr, index, all) => {
const dateObj = new Date(dateStr);
if (acc.length === 0) {
acc.push({ start: dateObj, prev: dateObj });
} else {
let last = acc[acc.length - 1];
const { start, prev } = last;
if (dateObj.getTime() - prev.getTime() <= DAY_MILLIS) {
last.prev = dateObj;
} else {
last.end = prev;
acc.push({ start: dateObj, prev: dateObj });
}
if (index === all.length - 1) {
last = acc[acc.length - 1];
if (last.end == null) {
last.end = last.prev;
}
}
}
return acc;
}, [])
.map(({ start, prev, end }) =>
((startStr, endStr) =>
startStr !== endStr ? [startStr, endStr] : [startStr])
(start.toISOString(), end.toISOString()));
console.log(ranges);
.as-console-wrapper { top: 0; max-height: 100% !important; }
Output
[
[ "2020-07-24T04:00:00.000Z", "2020-08-01T04:00:00.000Z" ],
[ "2020-11-29T05:00:00.000Z" ],
[ "2020-12-30T05:00:00.000Z", "2021-01-02T05:00:00.000Z" ],
[ "2021-02-18T05:00:00.000Z" ]
]

You can do the following using Array#reduce():
Go through each date.
Check if the current date will extend last range.
if yes, then overwrite the end in the range pair (second element)
if no, start a new range
If it happens that a range only has a single date, then use the start to compare with. The logic still holds - extending the range will add a second date. If the new date is not within the desired time frame, then a new range is created and the previous range is left with a single element in it.
const areDatesWithin = ms => (str1, str2) => {
if (!str1 || !str2)
return false;
const date1 = new Date(str1);
const date2 = new Date(str2);
return (date2 - date1) <= ms;
}
const areDatesWithin1Day = areDatesWithin(1000 * 60 * 60 * 24);
function combineInRanges(dates) {
return dates.reduce((acc, nextDate) => {
const lastDateRange = acc[acc.length-1] ?? [];
//compare with range end (if there) or range start
const lastDate = lastDateRange[1] ?? lastDateRange[0];
//check if the range needs to be extended
const mergeWithRange = areDatesWithin1Day(lastDate, nextDate);
if (mergeWithRange) {
//change the end of the range
lastDateRange[1] = nextDate;
} else {
//start a new range
acc.push([nextDate]);
}
return acc;
}, []);
}
const arr = ["2020-07-24T04:00:00.000Z", "2020-07-25T04:00:00.000Z", "2020-07-26T04:00:00.000Z", "2020-07-27T04:00:00.000Z", "2020-07-28T04:00:00.000Z", "2020-07-29T04:00:00.000Z", "2020-07-30T04:00:00.000Z", "2020-07-31T04:00:00.000Z", "2020-08-01T04:00:00.000Z", "2020-11-29T05:00:00.000Z", "2020-12-30T05:00:00.000Z", "2020-12-31T05:00:00.000Z", "2021-01-01T05:00:00.000Z", "2021-01-02T05:00:00.000Z", "2021-02-18T05:00:00.000Z"];
console.log(combineInRanges(arr));

https://stackoverflow.com/a/67182108/20667780
Jamiec answer is working. If you have a date array with UTC dates correctly offsetted to local timezone, then the daylight save start/end date will have more than 24 hours. You have to change the diffInHrs to 25 instead of 24.
Otherwise, its a perfect answer.

It's a sort of reduction based on the even-ness of the index...
let array = ['a', 'b', 'c', 'd', 'e', 'f'];
let pairs = array.reduce((acc, el, idx) => {
idx % 2 ? acc[acc.length-1].push(el) : acc.push([el]);
return acc;
}, []);
console.log(pairs)

How to compare consecutive date/time items in array and filter based on a specific time

I have the following array of objects:
var transactions = [
[
{"id":1,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:33:00.000Z"},
{"id":2,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:33:50.000Z"},
{"id":3,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:34:30.000Z"},
{"id":4,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:36:00.000Z"}
],
[
{"id":5,"sourceAccount":"A","targetAccount":"C","amount":250,"category":"other","time":"2018-03-02T10:33:00.000Z"},
{"id":6,"sourceAccount":"A","targetAccount":"C","amount":250,"category":"other","time":"2018-03-02T10:33:05.000Z"}
]
]
I need to compare time property of each object consecutively, and keep only those properties which time difference between each consecutive transaction is less than 1 minute.
The array format should be stay same, this is what I did try, but no luck, didn't work. What's the problem?
var newArray = transactions.map(g => g.reduce((r, o, i, a) => {
if (!i || new Date(o.time).getTime() - new Date(a[i - 1].time).getTime() >= 60000) {
r.push([o]);
} else {
r[r.length - 1].push(o);
}
return r;
}, []));
The expected output is something like this :
var output = [
[
{"id":1,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:33:00.000Z"},
{"id":2,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:33:50.000Z"},
{"id":3,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:34:30.000Z"}
],
[
{"id":5,"sourceAccount":"A","targetAccount":"C","amount":250,"category":"other","time":"2018-03-02T10:33:00.000Z"},
{"id":6,"sourceAccount":"A","targetAccount":"C","amount":250,"category":"other","time":"2018-03-02T10:33:05.000Z"}
]
]

You can Array#map your source array, and in each iteration, Array#filter the desired elements by comparing the time of current element with the time of previous element.
var transactions = [[{"id":1,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:33:00.000Z"},{"id":2,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:33:50.000Z"},{"id":3,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:34:30.000Z"},{"id":4,"sourceAccount":"A","targetAccount":"B","amount":100,"category":"food","time":"2018-03-02T10:36:00.000Z"}],[{"id":5,"sourceAccount":"A","targetAccount":"C","amount":250,"category":"other","time":"2018-03-02T10:33:00.000Z"},{"id":6,"sourceAccount":"A","targetAccount":"C","amount":250,"category":"other","time":"2018-03-02T10:33:05.000Z"}]];
var result = transactions.map((tr, i) => {
return tr.filter((t, j) => {
if (transactions[i][j - 1]) {
var d1 = new Date(t.time);
var d2 = new Date(transactions[i][j - 1].time);
return (d1.getTime() - d2.getTime()) <= 60000;
}
return true;
});
});
console.log(result);

I need to sort an array in descending order based on date [duplicate]

This question already has answers here:
How to sort an object array by date property?
(25 answers)
Closed 4 years ago.
Here's my code:
function getDetailsForShipmentId() {
//Fill code here
var strTable="<table id='myTable' border='2'><tr><th>Shipment Number</th><th>Port</th><th>Date</th><th>Time</th><th>Status</th></tr>";
var array=[];
array=populateShipmentDetails();
array.sort(sortFunction);
var i, found, obj;
var id=document.getElementById("shipmentId").value;
for (i = 0; i < array.length; i++) {
obj = array[i];
if (obj.shipmentId == id) {
strTable+="<tr><td>"+obj.shipmentId+"</td><td>"+obj.port+"</td><td>"+obj.date+"</td><td>"+obj.time+"</td><td>"+obj.status+"</td></tr>";
}
}
strTable+="</table>";
document.getElementById("result").innerHTML=strTable;
}
function sortFunction(a,b){
var dateA = new Date(a.date).getTime();
var dateB = new Date(b.date).getTime();
return dateA > dateB ? 1 : -1;
};
I am able to get the result searching through the javascript array but the sorting is not happening. Could somebody help?
Here's my output:

You can use this function to sort the array by the key
/**
* Sort object properties (only own properties will be sorted).
* #param {object} obj object to sort properties
* #param {string|int} sortedBy 1 - sort object properties by specific value.
* #param {bool} isNumericSort true - sort object properties as numeric value, false - sort as string value.
* #param {bool} reverse false - reverse sorting.
* #returns {Array} array of items in [[key,value],[key,value],...] format.
*/
function sortProperties(obj, sortedBy, isNumericSort, reverse) {
sortedBy = sortedBy || 1; // by default first key
isNumericSort = isNumericSort || false; // by default text sort
reverse = reverse || false; // by default no reverse
var reversed = (reverse) ? -1 : 1;
var sortable = [];
for (var key in obj) {
if (obj.hasOwnProperty(key)) {
sortable.push([key, obj[key]]);
}
}
if (isNumericSort)
sortable.sort(function (a, b) {
return reversed * (a[1][sortedBy] - b[1][sortedBy]);
});
else
sortable.sort(function (a, b) {
var x = a[1][sortedBy].toLowerCase(),
y = b[1][sortedBy].toLowerCase();
return x < y ? reversed * -1 : x > y ? reversed : 0;
});
return sortable; // array in format [ [ key1, val1 ], [ key2, val2 ], ... ]
}
using the function would be as below
sortProperties(array, 'date', true, false);

You need to convert your date from DD/MM/YYYY to YYYY/MM/DD format. Then, using localeCompare you can sort the dates.
const dates = ['01/07/2017','29/05/2017', '29/06/2017', '01/07/2017', '30/06/2017', '30/06/2017'];
const conversion = (date) => date.split('/').reverse().join();
dates.sort((a,b) => {
const dateA = conversion(a),
dateB = conversion(b);
return dateA.localeCompare(dateB);
});
console.log(dates);

Counting array elements with specific date in javascript

I have an array of Date() objects in javascript and I want to count the number of events on each day.
Here is an example:
What I have is:
Array [ Date 2014-12-04T10:30:20.000Z, Date 2014-12-05T11:04:58.056Z, Date 2014-12-05T11:04:58.056Z, Date 2014-12-05T11:04:58.056Z ]
What I want is:
Array [{date: '2014-12-04', counts: 1}, {date: '2014-12-05', counts: 3}]
Thanks a lot!
Max

Basic answer:
var arr = [], // fill it with array with your data
results = {}, rarr = [], i, date;
for (i=0; i<arr.length; i++) {
// get the date
date = [arr[i].getFullYear(),arr[i].getMonth(),arr[i].getDate()].join("-");
results[date] = results[date] || 0;
results[date]++;
}
// you can always convert it into an array of objects, if you must
for (i in results) {
if (results.hasOwnProperty(i)) {
rarr.push({date:i,counts:results[i]});
}
}
These can be made much easier with lodash functions, and Array.forEach() in ES5

You much better off having a simple object with the keys as the date and the value as the count. I've added a simple pad function that prefixes a zero where the number is a single digit as per your output requirements.
function pad(n) {
return n.toString().length == 1 ? '0' + n : n;
}
function getCount(arr) {
var obj = {};
for (var i = 0, l = arr.length; i < l; i++) {
var thisDate = arr[i];
var day = pad(thisDate.getDate());
var month = pad(thisDate.getMonth() + 1);
var year = thisDate.getFullYear();
var key = [year, day, month].join('-');
obj[key] = obj[key] || 0;
obj[key]++;
}
return obj;
}
getCount(arr); // Object { 2014-04-12: 1, 2014-05-12: 3 }
DEMO

I came across the same issue and found this solution which uses Map()
`
calc = (obj) => {
const orders = []
const dates_map = new Map()
//iterate through all the objects inside the orders array
orders.forEach(order => {
// format and get the date
const date = new Date(order.created_at).toLocaleDateString('en-GB')
//check if the date key exists in the Map() and save it in a temp
const temp = dates_map.get(date) || false
// if it does not exist
if (temp) {
// clone the object
const previous = {...temp}
// increase counter
previous.count += 1
dates_map.set(date, previous)
}else{
//create new object to avoid overwriting
const result = {}
result.count = 1
dates_map.set(date, result)
}
})
console.log(dates_map)
}
And this is the output
Output: Map(3) {
'08/05/2021' => { count: 2 },
'09/05/2021' => { count: 1 },
'11/05/2021' => { count: 2,}
}
`

Comparing an array of time with a time in javascript

I have an array of time that I get from the database and pass it to the javascript.when I alert the array variable I get the array of times(in my case 2 different times say 12:00 and 14:30),let the array be newdate.
In the javascript I also take in the another time say date=(12:00) I want to compare both the timings.both the values in newdate compare with date.
How to do it?
I tried the following
var newdate = new Array();
newdate = $('#newdate').val();
for(i=0;i<newdate.length;i++) {
alert(newdate[i]);
}
if (newdate >= date) {
alert("enable");
}
else {
alert("disbale");
}
when I ALERT the above I get 1,2,:,0,0 which is wrong,I want 12:00

Problem
Consider the following samples :
var string = '12:30';
for (var i = 0; i < string.length; i++) {
console.log(string[i]); // will print each character separately
}
var array = ['12:30']; // array of strings
for (var i = 0; i < array.length; i++) {
console.log(array[i]); // will print "12:30"
}
In the first case, replacing '12:30' with ['1', '2', ':', '3', '0'] will give the same result, in other words, looping through a string is like looping through an array of characters. Knowing that, let's return back to your own code :
// newdate is an empty array -> []
var newdate = new Array();
// ... then newdate is overwritten with a string -> "12:00"
newdate = $('#newdate').val();
// ... then newdate is traversed -> ["1", "2", ":", "0", "0"]
Solution
Here is how you could test a time against a collection :
var temp, item, gte;
var time = '12:15';
var collection = ['12:45', '12:00', '12:15', '12:30', '13:00', '11:00'];
var temp = time.split(':');
for (var i = 0; i < collection.length; i++) {
item = collection[i].split(':');
gte = +temp[0] >= +item[0];
if (gte) gte = +temp[1] >= +item[1];
// if (gte) gte = +temp[2] >= +item[2]; // uncomment to check seconds
if (gte) alert(time + ' >= item #' + i);
}
The above code will alert three times :
12:15 >= item #1
12:15 >= item #2
12:15 >= item #5
Going further
Reduces the collection to times that pass the function's test :
function filter(collection, fn) {
var i = 0,
l = collection.length,
result = [],
item;
for (; i < l; i++) {
item = collection[i];
if (fn(item, i)) result.push(item);
}
return result;
}
Returns a test function for times greater than or equal to the passed one :
function gte(time) {
time = time.split(':');
return function (item) {
item = item.split(':');
return +time[0] < +item[0] || (
+time[0] === +item[0] && +time[1] <= +item[1]
);
};
}
Returns a test function for times lower than or equal to the passed one :
function lte(time) {
time = time.split(':');
return function (item) {
item = item.split(':');
return +time[0] >= +item[0] && +time[1] >= +item[1];
};
}
Usage examples :
var collection = ['12:45', '12:00', '12:15', '12:30', '13:00', '11:00'];
var gteNoon = filter(collection, gte('12:00'));
var lteNoon = filter(collection, lte('12:00'));
var aroundNoon = filter(collection, function (time) {
return time.slice(0, 2) === '12';
});
gteNoon; // ["12:45", "12:00", "12:15", "12:30", "13:00"]
lteNoon; // ["12:00", "11:00"]
aroundNoon; // ["12:45", "12:00", "12:15", "12:30"]