How can I create a hash table object in JavaSript and use a date as the key? So far I've got this:
var eventHash = {};
for (var i = 0, l = events.length; i < l; i += 1) {
eventHash[events[i].date.getTime()] = events[i];
}
And then when I want to find the event associated with today I would use this:
var event = eventHash[(new Date(2011, 04, 26, 0, 0, 0, 0)).getTime()];
Can anyone see any pitfalls with this solution, or have any suggestions for improvement?
Why wouldn't you just use an ISO8601 representation of the date, so the key would be like 20110426. Creating a date object seems a bit inefficient.
It would also make debugging easier as the property names are more human readable, even if you add hhmmss also.
The only issue I see is that it's pretty limiting if you suddenly need to have multiple events with the same date. Otherwise it should be alright.
Also: Today is May 23, not Apr 26 :)
I have a somewhat similar problem and my solution may help others.
I have a list of "entries", each entry has a timestamp and a value.
I want to divide them up into "buckets", one for each day.
In Python I would have used collections.defaultdict but since JavaScript does not have something like that I do the following.
If you want to read the keys, remember that when you use a Date as an object key it gets converted as a string.
var get_entries = function() {
var entries = [];
entries.push({
'timestamp': 1381831606,
'value': 3
});
entries.push({
'timestamp': 1381831406,
'value': 2
});
entries.push({
'timestamp': 1381531606,
'value': 6
});
entries.push({
'timestamp': 1381221606,
'value': 9
});
entries.push({
'timestamp': 1381221601,
'value': 8
});
entries.push({
'timestamp': 1381221656,
'value': 7
});
return entries;
};
var normalize_date = function(timestamp) {
// JavaScript timestamps work with milliseconds.
var dt = new Date(timestamp * 1000);
return new Date(
dt.getFullYear(),
dt.getMonth(),
dt.getDate()
);
};
var prepare_data = function() {
var entry,
line = {};
var entries_raw = get_entries();
for (var i = 0; i < entries_raw.length; i++) {
entry = entries_raw[i];
entry.date = normalize_date(entries_raw[i].timestamp);
// If date not exists in line, create it.
console.log('Found entry for date', entry.date, 'with value', entry.value);
if (typeof(line[entry.date]) === 'undefined'){
line[entry.date] = 0;
}
line[entry.date] += entry.value;
}
console.log(line);
return line;
};
prepare_data();
Output:
$ nodejs diaryindex.js
Found entry for date Tue Oct 15 2013 00:00:00 GMT+0200 (CEST) with value 3
Found entry for date Tue Oct 15 2013 00:00:00 GMT+0200 (CEST) with value 2
Found entry for date Sat Oct 12 2013 00:00:00 GMT+0200 (CEST) with value 6
Found entry for date Tue Oct 08 2013 00:00:00 GMT+0200 (CEST) with value 9
Found entry for date Tue Oct 08 2013 00:00:00 GMT+0200 (CEST) with value 8
Found entry for date Tue Oct 08 2013 00:00:00 GMT+0200 (CEST) with value 7
{ 'Tue Oct 15 2013 00:00:00 GMT+0200 (CEST)': 5,
'Sat Oct 12 2013 00:00:00 GMT+0200 (CEST)': 6,
'Tue Oct 08 2013 00:00:00 GMT+0200 (CEST)': 24 }
Related
I have the following code using Google Apps Script, but when I log it out I get the following results. I want GAS to log the next month and stop once it gets to "lastDateofYear ". For whatever reason, the year doesn't change in my results, it just keeps repeating the current year. Please help.
var thisDate = "Mon Dec 20 00:00:00 GMT-06:00 2021";
var nextYear = Number(currentYear)+1;
var lastDateofYear = new Date("12-31-"+nextYear);
for(var i=thisDate; i <= lastDateofYear; ){
var currentiDate = new Date(i);
var month = currentiDate.getMonth()+1;
i.setMonth((month) % 12);
i.setDate(currentiDate.getDate());
Logger.log(currentiDate);
}
RESULTS:
Mon Dec 20 00:00:00 GMT-06:00 2021
Wed Jan 20 00:00:00 GMT-06:00 2021
Sat Feb 20 00:00:00 GMT-06:00 2021
Sat Mar 20 00:00:00 GMT-05:00 2021
Tue Apr 20 00:00:00 GMT-05:00 2021
Thu May 20 00:00:00 GMT-05:00 2021
Sun Jun 20 00:00:00 GMT-05:00 2021
Tue Jul 20 00:00:00 GMT-05:00 2021
Fri Aug 20 00:00:00 GMT-05:00 2021
Mon Sep 20 00:00:00 GMT-05:00 2021
Wed Oct 20 00:00:00 GMT-05:00 2021
Sat Nov 20 00:00:00 GMT-06:00 2021
Mon Dec 20 00:00:00 GMT-06:00 2021
Wed Jan 20 00:00:00 GMT-06:00 2021
Sat Feb 20 00:00:00 GMT-06:00 2021
Sat Mar 20 00:00:00 GMT-05:00 2021
Tue Apr 20 00:00:00 GMT-05:00 2021
As I understand it, you want to print each month from the given date to the last month of the next year of the given date in the log.
You can do this in the following code:
let start = new Date("Mon Dec 20 00:00:00 GMT-06:00 2021");
let currentYear = new Date().getFullYear();
let nextYear = currentYear + 1;
let end = new Date(nextYear, 11, 31);
while (start <= end) {
// You can use Logger.log() here if you want. I use console.log() for demo purpose
console.log(new Date(start).toDateString());
start.setMonth(start.getMonth() + 1);
}
If I got any part wrong, feel free to point it out to me in the comments.
There is a lot to say about your code:
var thisDate = "Mon Dec 20 00:00:00 GMT-06:00 2021";
That timestamp format is not supported by ECMA-262, so don't use the built–in parser to parse it, see Why does Date.parse give incorrect results?
var nextYear = Number(currentYear)+1;
Where does currentYear come from?
var lastDateofYear = new Date("12-31-"+nextYear);
Parsing of an unsupported format, see above. In Safari it returns an invalid date.
for(var i=thisDate; i <= lastDateofYear; ){
Sets i to the string value assigned to thisDate. Since lastDateOfYear is an invalid date in Safari and Firefox, so the test i <= NaN is never true and the loop is never entered.
var currentiDate = new Date(i);
Parses i, see above.
var month = currentiDate.getMonth()+1;
i.setMonth((month) % 12);
i is a string, which doesn't have a setMonth method so I'd expect a Type error like "i.setMonth is not a function" if the loop actually runs.
i.setDate(currentiDate.getDate());
Another Type error as above (but it won't get this far).
Logger.log(currentiDate);
}
It seems you want to sequentially add 1 month to a date until it reaches the same date in the following year. Trivially, you can just add 1 month until you get to the same date next year, something like:
let today = new Date();
let nextYear = new Date(today.getFullYear() + 1, today.getMonth(), today.getDate());
let result = [];
do {
result.push(today.toString());
today.setMonth(today.getMonth() + 1);
} while (today <= nextYear)
However, adding months is not that simple. If you add 1 month to 1 Jan, you'll get 2 or 3 Mar depending on whether it's a leap year or not. And adding 1 month to 31 Aug will return 1 Oct.
Many "add month" functions check to see if the date rolls over an extra month and if it does, set the date back to the end of the previous month by setting the date to 0, so 31 Jan + 1 month gives 28 or 29 Feb.
But if you cycle over a year using that algorithm, you'll get say 31 Jan, 28 Feb, 28 Mar, 28 Apr etc. rather than 31 Jan, 28 Feb, 31 Mar, 30 Apr, etc.
See JavaScript function to add X months to a date and How to add months to a date in JavaScript?
A more robust way is to have a function that adds n months to a date and increment the months to add rather than the date itself so the month–end problem can be dealt with separately for each addition, e.g.
/* Add n months to a date. If date rolls over an extra month,
* set to last day of previous month, e.g.
* 31 Jan + 1 month => 2 Mar, roll back => 28 Feb
*
* #param {number} n - months to add
* #param {Date} date - date to add months to, default today
* #returns {Date} new Date object, doesn't modify passed Date
*/
function addMonths(n, date = new Date()) {
let d = new Date(+date);
let day = d.getDate();
d.setMonth(d.getMonth() + n);
if (d.getDate() != day) d.setDate(0);
return d;
}
/* return array of n dates at 1 month intervals. List is
* inclusive so n + 1 Dates returned.
*
* #param {Date} start - start date
* #param {number} n - number of months to return
* #returns {Array} array of Dates
*/
function getMonthArray(n, start = new Date()) {
let result = [];
for (let i=0; i<n; i++) {
result.push(addMonths(i, start));
}
return result;
}
// Examples
// Start on 1 Dec
getMonthArray(12, new Date(2021,11,1)).forEach(
d => console.log(d.toDateString())
);
// Start on 31 Dec
getMonthArray(12, new Date(2021,11,31)).forEach(
d => console.log(d.toDateString())
);
The functions don't attempt to parse timestamps to Dates, that responsibility is left to the caller.
I have an object like this:
times = {
"dawn": "Mon Jul 06 2020 01:34:46 GMT+0200 (Mitteleuropäische Sommerzeit)",
"dusk": "Mon Jul 06 2020 22:43:02 GMT+0200 (Mitteleuropäische Sommerzeit)",
"evening": "Mon Jul 06 2020 19:06:36 GMT+0200 (Mitteleuropäische Sommerzeit)",
"morning": "Mon Jul 06 2020 08:02:55 GMT+0200 (Mitteleuropäische Sommerzeit)"
};
I want to compare the current time with this object and want to get the key as return value, which is closest to the current time.
I try to use this function, but I never get the right key back.
function getKeyByValue(object, value) {
return Object.keys(object).find(key => object[key] === value || object[key] < value);
}
let date = new Date();
getKeyByValue(times, date);
What do I have to change for this to work?
There are two problems here:
You're comparing strings, not dates. Use Date.parse() to get a number, or new Date() to get a Date object.
You're only looking for the first matching value with .find(), not the closest. You'll have to use a more custom solution to find the closest.
This will find the time before the given time which is closest:
// Just so this example works in the future, while still
// comparing against the current time:
const makeTime = (h, m) => {
const today = new Date();
return new Date(today.getFullYear(), today.getMonth(), today.getDate(), h, m);
}
const times = {
"dawn": makeTime(05, 00), // 5:00am
"morning": makeTime(07, 00), // 7:00am
"afternoon": makeTime(12, 00), // 12:00pm
"late afternoon": makeTime(17, 00), // 5:00pm
"dusk": makeTime(19, 00), // 7:00pm
"evening": makeTime(20, 00), // 8:00pm
"night": makeTime(23, 00) // 11:00pm
};
// The important part is here:
const closestTime = Object.entries(times)
.map(([k, v]) => [ k, Date.now() - Date.parse(v) ])
.reduce((pre, cur) => cur[1] < pre[1] && cur[1] > 0 ? cur : pre)[0];
console.log(`Right now, it is ${closestTime}.`);
Here's how it works:
// Get a list of [ key, value ] lists for every key and value in `times`.
const closestTime = Object.entries(times)
// Turn that list of [ key, value ] and turn it into a list of keys and
// the differences between compareTime and the date in the value. Values
// in the future create negative numbers, since their Unix Epoch
// representation is larger than the compared time.
// IE: [ [ 'morning', 12300000 /* (seconds) */ ], ... ]
.map(([k, v]) => [ k, Date.now() - Date.parse(v) ])
// Run through that list, keeping track of the current value only if it
// is smaller than the previous value and positive.
.reduce((pre, cur) => cur[1] < pre[1] && cur[1] > 0 ? cur : pre)
// ↑ returns [ key, value ], and we just want `key`.
[0];
If you want to compare against a specific time, replace Date.now() with Date.parse() and pass in a date string, like Date.parse('Jul 07 2020 11:25:00').
You need to parse the dates in your times object.
Currently, JavaScript is just seeing them as strings so you're comparing a string to a number which returns false.
Try using Date.parse(object[key]). This returns a number.
Convert them to date objects, get the smallest delta, iterate em.
var times = {
"dawn": "Mon Jul 06 2020 01:34:46 GMT+0200 (Mitteleuropäische Sommerzeit)",
"dusk": "Mon Jul 06 2020 22:43:02 GMT+0200 (Mitteleuropäische Sommerzeit)",
"evening": "Mon Jul 06 2020 19:06:36 GMT+0200 (Mitteleuropäische Sommerzeit)",
"morning": "Mon Jul 06 2020 08:02:55 GMT+0200 (Mitteleuropäische Sommerzeit)"
};
var closestKey = null;
var closestDelta = null;
for(key in times)
{
var delta = Math.abs(Date.now() - Date.parse(times[key]));
if(delta < closestDelta || closestDelta == null)
{
closestKey = key;
closestDelta = delta;
}
}
console.log("The closest is:" + closestKey);
Please check it out
times = {
"dawn": "Mon Jul 06 2020 01:34:46 GMT+0200 (Mitteleuropäische Sommerzeit)",
"dusk": "Mon Jul 06 2020 22:43:02 GMT+0200 (Mitteleuropäische Sommerzeit)",
"evening": "Mon Jul 06 2020 19:06:36 GMT+0200 (Mitteleuropäische Sommerzeit)",
"morning": "Mon Jul 06 2020 08:02:55 GMT+0200 (Mitteleuropäische Sommerzeit)"
};
let obj = {}
for (time in times){
Object.assign(obj, {[time]:Math.abs(new Date() - new Date(times[time]).getTime())});
}
//console.log(obj)
function closestDate(obj){
let closestVal = Math.min(...Object.values(obj))
for (item in obj){
if(obj[item] === closestVal){
return item;
}
}
}
console.log(closestDate(obj));
I have the following string value of a date, Sun Apr 07 2019 00:00:00 GMT-0300, and I need to compare with the following date format 2019-04-08T03:00:00.000Z, note that both are the same day, I need to compare them and return a true as being equal days,
but I do not know how to do this using javascript, any help?
I tried to do something like this but it does not return me true:
if (input) {
//input.value = "Sun Apr 07 2019 00:00:00 GMT-0300 (Horário Padrão de Brasília)"
var situation = angular.isArray(item.situation) ? item.situation : [item.situation];
// situation =
//[
// 0: "2019-04-08T03:00:00.000Z"
// 1: "2019-04-13T03:00:00.000Z"
//]
if (!angular.isArray(input.value)) {
condition = situation.indexOf(input.value) >= 0;
} else if (angular.isArray(input.value)) {
condition = $window._.intersection(situation, input.value).length > 0;
}
}
if (condition) {
break;
}
//input.value = "Sun Apr 07 2019 00:00:00 GMT-0300 (Horário Padrão de Brasília)"
situation =
[
0: "2019-04-08T03:00:00.000Z"
1: "2019-04-13T03:00:00.000Z"
]
Sun Apr 07 2019 00:00:00 GMT-0300
2019-04-08T03:00:00.000Z
note that both are the same day
No, they are not.
You can convert them both to ISO string and just compare their date parts as strings (if I understood the question correctly, you want to compare date only, without time):
function isSameDate(date1, date2) {
const [d1, ] = (new Date(date1)).toISOString().split('T');
const [d2, ] = (new Date(date2)).toISOString().split('T');
return d1 === d2;
}
Convert all the values to Date objects and compare those. Use a framework/library to do it, because parsing strings to dates manually has lots of places where it can go wrong.
Currently you are comparing the literal Strings. Because neither "2019-04-08T03:00:00.000Z", nor "2019-04-13T03:00:00.000Z" match "Sun Apr 07 2019 00:00:00 GMT-0300 (Horário Padrão de Brasília)", your second if statement fails.
Build a date from the strings and compare the days (ie number of seconds since epoch / number of seconds in a day):
const sameDay = (dateString1, dateString2) => {
let time1 = (new Date(dateString1)).getTime();
let time2 = (new Date(dateString2)).getTime();
return Math.floor(Math.abs((time1-time2))/(1000*60*60*24))==0;
}
console.log(
sameDay('Sun Apr 07 2019 00:00:00 GMT-0300 (Horário Padrão de Brasília)','2019-04-08T03:00:00.000Z'),
sameDay('Sun Apr 07 2019 00:00:00 GMT-0300 (Horário Padrão de Brasília)','2019-04-13T03:00:00.000Z'),
);
I have two arrays of dates. The first one have all the booked dates and the second one will have dates between "start day" and "end day" which user will pick.
Now I have to confirm that the days between the start and stop will not be found from the fully booked dates array.
I'm using Vue.js to update data.
Here is what I have done to get those dates:
/**
* Get dates from datepicker and format it to the same format that fully booked array has it's dates.
**/
var day1 = moment( this.startDate, 'DD/MM/Y').format('Y,M,D');
var day2 = moment( this.endDate, 'DD/MM/Y').format('Y,M,D');
var start = new Date(day1);
var end = new Date(day2);
/**
* Get dates between start and stop and return them in the dateArray.
**/
Date.prototype.addDays = function(days) {
var dat = new Date(this.valueOf());
dat.setDate(dat.getDate() + days);
return dat;
};
function getDates(startDate, stopDate) {
var dateArray = [];
var currentDate = startDate;
while (currentDate <= stopDate) {
dateArray.push(currentDate);
currentDate = currentDate.addDays(1);
}
return dateArray;
}
var dateArray = getDates(start, end);
/**
* Set dateArray in to Vue.js data.
**/
this.$set('daysBetweenStartStop', dateArray);
/**
* Get arrays of dates from the Vue.js data. calendar = Booked dates | matchingDays = Dates between start and stop.
**/
var calendar = this.fullDates;
var matchingDays = this.daysBetweenStartStop;
/**
* #description determine if an array contains one or more items from another array.
* #param {array} haystack the array to search.
* #param {array} arr the array providing items to check for in the haystack.
* #return {boolean} true|false if haystack contains at least one item from arr.
*/
var findIfMatch = function (haystack, arr) {
return arr.some(function (v) {
return haystack.indexOf(v) >= 0;
});
};
var matching = findIfMatch(calendar, matchingDays);
/**
* Check the results. If false we are good to go.
**/
if (matching){
alert('WE FOUND A MATCH');
} else {
alert('GOOD TO GO');
}
Arrays are in the following format:
var calendar = [
Sun Oct 02 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 09 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 16 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 23 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 30 2016 00:00:00 GMT+0300 (EEST)
]
var matchingDays = [
Fri Oct 28 2016 00:00:00 GMT+0300 (EEST),
Sat Oct 29 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 30 2016 00:00:00 GMT+0300 (EEST)
]
My problem is that even if those two arrays have exactly same dates they will still somehow be considered as a not identical. Any ideas how to get this working?
Your match function should look like this :
findIfMatch = function (haystack, arr){
var i = 0;//array index
var j = 0;//array index
while(j < arr.length && i < haystack.length){
cur_cal = Date.parse(haystack[i]);
cur_match = Date.parse(arr[j]);
if(cur_cal > cur_match){
j++;
}else if(cur_cal < cur_match){
i++;
}else{
return true;
}
}
return false;
}
To get matching records from two array use this
var calendar = [
Sun Oct 02 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 09 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 16 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 23 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 30 2016 00:00:00 GMT+0300 (EEST)
];
var matchingDays = [
Fri Oct 28 2016 00:00:00 GMT+0300 (EEST),
Sat Oct 29 2016 00:00:00 GMT+0300 (EEST),
Sun Oct 30 2016 00:00:00 GMT+0300 (EEST)
];
var newCalendar = [];
var newMatchingDays = []
$.map(calendar, function(date){
newCalendar.push(date.toString())
});
$.map(matchingDays, function(date){
newMatchingDays.push(date.toString())
});
var result = [];
$.map(newCalendar, function (val, i) {
if ($.inArray(val, newMatchingDays) > -1) {
result.push(val);
}
});
console.log(result);
Firstly you can't compare dates like that, Date is an object.
eg.
var d1 = new Date('2016-09-30');
var d1 = new Date('2016-09-30');
console.log(d1 === d2); // = false
You would need to loop the array and compare each item, rather than use indexOf.
or maybe use the Array.filter(). Or alternatively use and object as a lookup.
eg. If say you had ->
var calendar = {
"Sun Oct 02 2016 00:00:00 GMT+0300 (EEST)": true,
"Sun Oct 09 2016 00:00:00 GMT+0300 (EEST)": true,
"Sun Oct 16 2016 00:00:00 GMT+0300 (EEST)": true,
"Sun Oct 23 2016 00:00:00 GMT+0300 (EEST)": true,
"Sun Oct 30 2016 00:00:00 GMT+0300 (EEST)": true
};
if (calendar["Sun Oct 16 2016 00:00:00 GMT+0300 (EEST)"]) {
console.log("We have date");
}
Notice how I use a string representation for the date, this could be a number too, eg. from Date.getTime().
Here is using Array.filter, I don't think it's as fast a Object lookup's. But here we go.
var calendar = [
new Date('2016-09-01'),
new Date('2016-09-12'),
new Date('2016-09-10')
];
var finddate = new Date('2016-09-12');
var found = calendar.filter(function (a) { return a.getTime() === finddate.getTime();});
And if you don't mind using third party library, try underscore..
eg.
var days = [new Date('2016-09-01'), new Date('2016-09-10'), new Date('2016-09-30')];
var finddays = [new Date('2016-09-01'), new Date('2016-09-30')];
var found = _.intersectionWith(days, finddays,
function (a,b) { return a.getTime() === b.getTime(); });
I want to get all dates between a startDate and an endDate.
I wrap the startDate/endDate with moment() again to clone the start/endDate because they must not be changed.
But still the getDateRange gives me odd results about dates:
testCase.startDate = moment(new Date(2014, 0, 1));
testCase.endDate = moment(new Date(2014, 0, 27));
Although both dates are in 2014 I get a dateRange from december 2013 days?
Why is that?
function getDateRange(startDate, endDate) {
return Enumerable.range(0, moment(endDate).diff(moment(startDate), 'days') + 1)
.select(function (offset) {
return moment(startDate).add(offset, 'days')
})
.toArray();
}
UPDATE
Your query looks like it should work. Maybe you're interpreting the dates incorrectly. Remember, only the month starts at 0. Maybe you offset the year too when you looked at the values.
Here's an alternate way you can write the query:
function getDateRange(startDate, endDate) {
return Enumerable.Unfold(startDate, "moment($).add(1, 'd')")
.TakeWhile(function (d) { return d <= endDate; })
.ToArray();
}
Based on what I'm seeing in the comments, it appears you're using methods which mutates the dates. You'll either want to avoid using these methods or clone the date first and manipulate the clones.
// without cloning
var date1 = moment.utc([2014, 0, 1]);
console.log(String(date1)); // Wed Jan 01 2014 00:00:00 GMT+0000
var startOfDate1 = date1.startOf('week'); // mutated
console.log(String(date1)); // Sun Dec 29 2013 00:00:00 GMT+0000
// using moment()
var date2 = moment.utc([2014, 0, 1]);
console.log(String(date2)); // Wed Jan 01 2014 00:00:00 GMT+0000
var startOfDate2 = moment(date2).startOf('week'); // not mutated
console.log(String(date2)); // Wed Jan 01 2014 00:00:00 GMT+0000
// using clone()
var date3 = moment.utc([2014, 0, 1]);
console.log(String(date3)); // Wed Jan 01 2014 00:00:00 GMT+0000
var startOfDate3 = date3.clone().startOf('week'); // not mutated
console.log(String(date3)); // Wed Jan 01 2014 00:00:00 GMT+0000