I have to calculate X working days before a date in javascript. I have an array of holidays, how can I do this?
I can make a while loop with my date and change it to the previous day and check if it's a business day then increment my variable but is it a good way to do this?
In normal languages you could easily solve this with a hashset. It has vary fast look up times, and random access.
However, Javascript isn't like all the other children. So it has it's own special way of doing this. The easiest way is just an object.
var holidays = {
1:true,
7:true,
18:true
}
I use days since newyear, but there isn't anything wrong with using a date or something else.
Then you can make a little helper function:
var checkDate = function(value){
return holidays [value] === true;
};
Then you just do checkDate(dayOfYear) and it will return true or false if it's a holiday. Then you can easily do
//This is more pseudocode than javascript, since I haven't done javascript in years
while checkDate(--dayOfYear === true)
previousBussinesDay = dayOfYear;
Or something similar to find the actual day.
Related
I am reading sleep data into my react-native app using react-native-healthkit, and I need to find a way to get the total amount of sleep time. The data is read in like this:
If anyone has any ideas on the best way to handle this data, please let me know.
extension Date {
/// Hours since current date to given date
/// - Parameter date: the date
func hours(since date: Date) -> Int {
let calendar = Calendar.current
let dateComponents = calendar.dateComponents([.hour], from: self, to: date)
return dateComponents.month ?? 0
}
}
date2.hours(since: date1)
Using .timeIntervalSince is a bad practice, because some hours may be shorter than other.
If anyone has any ideas on the best way to handle this data please let me know.
It really depends on how you're parsing that JSON data. I won't cover JSON parsing here because there are many, many tutorials and blog posts on that topic. Here's one in case you're not sure where to start.
Your goal is to end up with date objects (Date in Swift, NSDate in Objective-C). For example, if you have the values as strings, you can use DateFormatter to parse the strings into Date objects.
Once you have those date objects you can use the operations that those objects supply to get a TimeInterval, which is a double representing an interval in seconds. Convert that to hours by dividing by 3600:
let interval = endDate.timeIntervalSince(startDate)
let hours = interval / 3600
Try this
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"
guard let startDate = dateFormatter.date(from: "yourStartDate"),
let endDate = dateFormatter.date(from: "yourEndDate") else {
return
}
let difference = endDate.timeIntervalSince(startDate)
If you are targeting iOS 13 and above you can use
endDate.hours(since: startDate)
instead of timeInterval
I need to check if some date fields are greater then others.
I solved in this way for only one couple of dates. I can't find a solution for multiples couples of variables like these:
$scope.date1startFrom;
$scope.date1startTo;
$scope.date2startFrom;
$scope.date2startTo;
$scope.date3startFrom;
$scope.date3startTo;
I have to see the alert only if very element of the couple has a value. I find this solution but I want to extend it to multiple values but I can't.
var datesAreDefined = $scope.date1startFrom && $scope.date1startTo;
if (datesAreDefined && !periodFromAndToIsValid($scope.date1startFrom, $scope.date1startTo)) {
alert("error");
}
function periodFromAndToIsValid (from, to){
var fromDate = new Date(from).getTime();
var toDate = new Date(to).getTime();
return toDate >= fromDate;
}
I would recomend to use something like MomentJS its very effective for this case:
https://momentjs.com/
In this link you can find the way to make comparisons easily between dates.
https://momentjs.com/docs/#/query/
I know javascript is not the best way to go about this. I know that I would have to have the browser up and always running. I would normally do something with Python. This was a specific requests of me and i'm not very proficient with javascript. That being said.
I want the user to be able to set a time using inputs. Once these inputs have been set I want the browser to check for the time specified. Once the time occurs I want it to execute a command.
Her is what I have so far:
<html>
<body>
<p>Enter Time to start dashboard</p>
<p>Hour</p>
<input id="strthour">
<p>Minute</p>
<input id="strtmin">
<button onclick="setTime()">Submit</button>
<script>
var hr = 06; //default time of 6am to run
var mn = 00;
function setTime() {
hr = strthour.value;
mn = strtmin.value;
}
window.setInterval(function(){ // Set interval for checking
alert(hr+mn);
var date = new Date(); // Create a Date object to find out what time it is
if(date.getHours() === hr && date.getMinutes() === mn && date.getSeconds() === 0){ // Check the time
alert("it worked")
}
}, 5000); // Repeat every 60000 milliseconds (1 minute)
</script>
</body>
</html>
I am able to change the global variables, but I am unable to get window.setInterval to recognize the changes. Any advice?
Here is a link to a JSFiddle I made.
There are several issues with your code, which various people have pointed out.
Walker Randolph Smith correctly notes that date.GetHours() and date.getMinutes() will both return numbers, while the values returned from strthour.value and strtmin.value will be strings. When JavaScript compares these two, it will always evaluate to false. To fix this, try running the user input through parseInt, as in hr = parseInt(strthour.value, 10);. The 10 is important because it tells parseInt to create a number of base 10 (you don't need to know what that means, just make sure to include the 10).
Your need for the seconds to match is probably unnecessary, and does not match up with the interval you chose. TheMintyMate made this correction in their code snippet by simply removing the comparison for seconds. If you really need to make sure the seconds match up perfectly, pick an interval of less than 1000 milliseconds, so you know it is going to check at least once every second, guaranteeing that you will run the check on that 0th second of the desired time.
You could run into some trouble with single digit minutes if you try to compare them as strings, rather than converting to numbers as recommended in point 1. The .getMinutes() method will return a single digit 0 for a time like 6:00, while your example is implicitly prompting the user to enter in two digits for that same time. Again, you can avoid this issue entirely by using parseInt as recommended in point #1.
I do have to throw in a plug for using Cron jobs for running tasks on a known schedule like this. I know you said the user requested JS in this case, so they may not apply for this specific situation. Since you didn't mention Cron jobs though, I have to include them here to make sure you and future readers are aware of them, because they are designed for exactly this situation of running a task on an automated schedule.
Good luck!
You are not correctly referring to the inputs, and you also have a syntax error with your alert. Below is my suggested fix (working):
<p>Enter Time to start dashboard</p>
<p>Hour</p>
<input id="strthour">
<p>Minute</p>
<input id="strtmin">
<button onclick="setTime()">Submit</button>
<script>
var hr = 0;
var mn = 0;
function setTime() {
hr = parseInt(document.getElementById("strthour").value);
mn = parseInt(document.getElementById("strtmin").value);
console.log("set time: "+hr+":"+mn);
}
setInterval(function(){
var date = new Date();
if(date.getHours() == hr && date.getMinutes() == mn){ // using == not ===
alert("it worked");
}
}, 10000);
</script>
Note: You should also parseInt() the values to ensure they are valid numbers.
if(date.getHours() === hr && date.getMinutes() === mn && date.getSeconds() === 0){ // Check the time
alert("it worked")
}
This will compare a string to an int and always be false.
either perform parseInt(date.getHours()) or use ==
It's not because setInterval doesn't recognize the change, you actually don't modify the values.
If you open the javascript console on jsfiddle page you'll see "Uncaught ReferenceError: setTime is not defined".
It will work if you define you setTime like this:
window.setTime = function() {
hr = strthour.value;
mn = strtmin.value;
}
This is because JSFiddle doesn't run your code directly, but wraps into
<script type='text/javascript'>//<![CDATA[
window.onload=function(){
... // you code here }
}//]]>
Here is a modified JSFiddle which just "it worked" for me.
Update - some notes, as mentioned in other answers:
The use of '===' is also an issue, hr/mn are strings, so you need '==' or convert hr/mn to integers
Expression like strthour.value in setTime works in JSFiddle. I am not really sure why, but it works. In the "real world" it should be something like document.getElementById("strthour").value
Update 2 - why does strthour.value work (vs document.getElementById("strthour").value)?
This was actually a surprise for me, but it looks like all major browsers put all elements with id into window object. More than that, it is actually a part of the HTML standard (although it is not recommended to use this feature):
6.2.4 Named access on the Window object
window[name]
Returns the indicated element or collection of elements.
As a general rule, relying on this will lead to brittle code. Which IDs end up mapping to this API can vary over time, as new features are added to the Web platform, for example. Instead of this, use document.getElementById() or document.querySelector().
References:
HTML 5.1 - 6.2.4 Named access on the Window object
Do DOM tree elements with ids become global variables?
Why don't we just use element IDs as identifiers in JavaScript?
I think you should use ">=" operator, because you don't know if it's gonna be EXACTLY that time.
We're trying to make an application that pairs users in a database every Wednesday and Friday. How is done in Meteor?
So in the server code I was thinking of putting this in a timedserver.js file
boolean hasMatched = false;
boolean isWednesday = false;
while(true){
if (day != Wednesday) isWednesday = false;
if (day == Wednesday){
matchUsers()
Wednesday = true;
}
setTimeOut(5 HOURS)
}
Is this how it should be approached? I'm not sure how to have continually running server code. Where do we put this code?
I would propose to use Meteor.setInterval() instead of using an infinite while-loop, and why not using an interval of 24 hours instead of 5?
Then you can check the weekday of the current date, e.g. with moment.js, and if it's wednesday or friday, run your code, at best asynchronously and non-blocking the interval.
I probably wouldn't use a while loop for something like this.
One package comes to mind though: synced-cron. It looks like it uses "Parsers" and there is quite a bit flexibility there.
Something like this would probably work:
SyncedCron.add({
name: 'Crunch some important numbers for the marketing department',
schedule: function(parser) {
// parser is a later.parse object
return parser.text('every Wednesday');
},
job: function() {
var matchedUsers = matchUsers();
return matchedUsers;
}
});
I've never uses this package, but I believe this code would fire every Wednesday.
May be using cron job will be better solution?
On a project I'm currently working on in JavaScript, I'm using decimal formats so it's easier to calculate with rather than using an hour/minute format in strings (calendar related project). To display the time on the user's screen though, the timecode has to be shown as hh:mm.
I thought it would be great to use a String prototype function for this as it would allow me to use code like:
var time = 8.75;
document.write("Meeting at "+time.toTime()); // writes: Meeting at 8:45
So far, I've got that almost working, using:
String.prototype.toTime = function(){
var hrs = this.toString().slice(0,this.indexOf("."));
var min = Math.round(this.toString().slice(this.indexOf("."))/100*60);
min = min<10 ? "0"+min : min.toString();
return hrs+":"+min;
}
The problem, though, is that this will only work if the variable time is a string. Otherwise it will give an undefined error.
Would there be any way of applying the prototype to a different object in JavaScript, so that I don't have to use time.toString().toTime()?
Thanks!
Firstly, you can add to the Number prototype. Many people will warn against modifying prototypes, which in many cases is justified. If there is a chance 3rd party scripts will be running alongside yours, it is a danger to modify prototypes.
Secondly, I simplified your code a little, using modulus, and floor to calculate the hrs and mins...
Number.prototype.toTime = function(){
var hrs = Math.floor(this)
var min = Math.round(this%1*60)
min = min<10 ? "0"+min : min.toString();
return hrs+":"+min;
}
var time = 8.25;
console.log("Meeting at "+time.toTime());
You can use Object.prototype.toTime.