Develop Reference

How can I get the value of a key from JSON to JS?

I'm working on an application that requires dates to be fed from JS and check in a JSON table what the "Letter" of the day is.
How can I take the JS date string that I've created (yyyy,mm,dd), and find the value of the corresponding key?
I have tried taking the string, stringifying it, and pushing it through a JS function.
var d = new Date();
var date = d.getDate();
var month = d.getMonth() + 1;
var year = d.getFullYear();
var dateStr = year + "/" + month + "/" + date;
console.log(dateStr);
dateJSON = JSON.stringify(dateStr)
console.log(dateJSON)
alert(testVar.dateJSON)
var testVar = { //In a JS file
"2019-11-06": "D",
"2019-11-08": "A_con" //continues for a very long time.....
}
For "2019-11-08" I would like to have variable "letterDay" equal "A_con".
My code thus far returns "undefined" when I pull "testVar.dateJSON"

I think it is far simpler than this, your data keys are in format yyyy-mm-dd while you're dateStr is in the format yyyy/mm/dd here is a simple snippet
var testVar = { //In a JS file
"2019-11-09": "D",
"2019-11-08": "A_con" //continues for a very long time.....
}
var d = new Date();
var date = d.getDate();
var month = d.getMonth() + 1;
var year = d.getFullYear();
// Your mistake was here, the separators were '/'
var dateStr = year + "-" + month + "-" + date;
console.log(dateStr);
// Get the value dynamically
// when you have a dynamic key use testVar[dateStr]
// testVar.dateStr will literally look for a key called "dateStr" it will not evaluate the value of dateStr
console.log(testVar[dateStr]);

You formatted your dateStr variable the wrong way ("/" instead of "-").
var testVar = { //In a JS file
"2019-11-06": "D",
"2019-11-08": "A_con" //continues for a very long time.....
}
var d = new Date('November 06, 2019 23:15:30');
var day = d.getDate();
var month = d.getMonth() + 1;
var year = d.getFullYear();
var dateStr = year + "-" + month + "-" + (day > 9 ? day : '0' + day);
console.log(testVar[dateStr]); // D

Have your tried using JSON.parse()?
So: JSON.parse(testVar); and then modify your code and variables from there.

Javascript - Generate date from daynumber

Say I have the day number of the year.
How can I generate the date from that?
EX. Today's day number is 265
How can I get the output 9/23/2015?
Yesterday's day number was 264, how can I get the output of 9/22/2015?

Try like this
var year = 2015;
var date = new Date(year,0,1); // get the first date of year
var numberOfDaysToAdd=264;
date.setDate(date.getDate() + numberOfDaysToAdd); // add days to that date
console.log(date);

You may simply use Date():
var days = 265;
var now = new Date();
now.setMonth(0); // jan
now.setDate(days);
var date = 1 + now.getMonth();
var pad = function(v) {
return 10 > v ? '0' + v : v;
};
date = pad(date) + '/' + pad(now.getDate()) + '/' + now.getFullYear();
document.write(date);

Convert UTC Date to dd/mm/yyyy Format

I am having some difficulties when trying to convert UTC Date format to dd/mm/yyyy in JavaScript:
var launchDate = attributes["launch_date"];
if (isBuffering) {
var date = new Date(launchDate);
var d = new Date(date.toLocaleDateString());
launchDate = ((d.getUTCMonth() + 1) + "/" + (d.getUTCDate() + 1) + "/" + (d.getUTCFullYear()));
}
I tried with this, but it returns me an invalid date. So I changed to this:
var launchDate = attributes["launch_date"];
if (isBuffering) {
var date = new Date(launchDate);
var d = formatDate(new Date(date.toLocaleDateString()));
launchDate = ((d.getUTCMonth() + 1) + "/" + (d.getUTCDate() + 1) + "/" + (d.getUTCFullYear()));
}
However, it still returning me invalid Date. I wonder is there any possible way to change the date format of Fri May 31 2013 17:41:01 GMT+0200 (CEST) to dd/mm/yyyy?
Thanks in advance.

var d = new Date();
var n = d.toLocaleDateString();
This will be more superior in build JS method!

function formatDate(d)
{
date = new Date(d)
var dd = date.getDate();
var mm = date.getMonth()+1;
var yyyy = date.getFullYear();
if(dd<10){dd='0'+dd}
if(mm<10){mm='0'+mm};
return d = dd+'/'+mm+'/'+yyyy
}

Try it:
Date.parseExact(Your_Date, 'dd/MM/yyyy').toString('MM/dd/yyyy');
or
Date.parseExact(Your_Date, 'MM/dd/yyyy').toString('dd/MM/yyyy');

Month is 0 indexed, but day is not. You don't need to add 1 to your day.
Also, you're formatting it for MM/dd/yyyy, not dd/MM/yyyy.
solution:
var launchDate = attributes["launch_date"];
if (isBuffering) {
var date = new Date(launchDate);
var d = formatDate(new Date(date.toLocaleDateString()));
launchDate = ((d.getUTCDate())+ "/" + (d.getUTCMonth() + 1) + "/" + (d.getUTCFullYear()));
}

Convert input type text into date format

I have one input type text:
<input type="text" id="policyholder-dob" name="policyholder-dob" />
I want to type number in this field in mm/dd/yyyy format:
like 01/01/2014
This is my js code but its not working, what mistake have I made?
function dateFormatter(date) {
var formattedDate = date.getDate()
+ '/' + (date.getMonth() + 1) + '/' + date.getFullYear();
return formattedDate;
}
var nextduedate = $("#policyholder-dob").val();
var dateFormatDate = nextduedate.slice(0, 2);
var dateFormatMonth = nextduedate.slice(2, 4);
var dateFormatYear = nextduedate.slice(4, 8);
var totalFormat = dateFormatMonth + '/' + dateFormatDate + '/' + dateFormatYear;
var againNewDate = new Date(totalFormat);
againNewDate.setDate(againNewDate.getDate() + 1);
var todaydate = dateFormatter(againNewDate);
$("#policyholder-dob").prop("value", todaydate);
Any help will be really appreciated.

Thankfully, your input is consistently in this format:
mm/dd/yyyy
So you can convert it to a Date object through a custom function, such as:
function stringToDate(str){
var date = str.split("/"),
m = date[0],
d = date[1],
y = date[2],
temp = [];
temp.push(y,m,d);
return (new Date(temp.join("-"))).toUTCString();
}
Or:
function stringToDate(str){
var date = str.split("/"),
m = date[0],
d = date[1],
y = date[2];
return (new Date(y + "-" + m + "-" + d)).toUTCString();
}
Etc..
Calling it is easy:
stringToDate("12/27/1963");
And it will return the correct timestamp in GMT (so that your local timezone won't affect the date (EST -5, causing it to be 26th)):
Fri, 27 Dec 1963 00:00:00 GMT //Late december
Example
There are various ways to accomplish this, this is one of them.

I'd suggest moment.js for date manipulation. You're going to run into a world of hurt if you're trying to add 1 to month. What happens when the month is December and you end up with 13 as your month. Let a library handle all of that headache for you. And you can create your moment date with the string that you pull from the val. You substrings or parsing.
var d = moment('01/31/2014'); // creates a date of Jan 31st, 2014
var duration = moment.duration({'days' : 1}); // creates a duration object for 1 day
d.add(duration); // add duration to date
alert(d.format('MM/DD/YYYY')); // alerts 02/01/2014
Here's a fiddle showing it off.

JavaScript Check Date not today or in the past

JavaScript Check Date not today or in the past.
var c = '10 JUN 2010'; // this is the format of the date coming in.
var temp = new Array();
temp = c.split(' ');
var x = new Date ( temp[1]+" "+temp[0]+", "+temp[2] );
if (x.getTime() > getDate()) {
alertstring = alertstring + '\n\nDEBUG CODE: 1 ' + x + '\n\n';
}
I cannot change the format coming in.

Looks like you 99% have it. Here it is with a modified if condition:
var c = '10 JUN 2010'; // this is the format of the date coming in.
var temp = new Array();
temp = c.split(' ');
var x = new Date ( temp[1]+" "+temp[0]+", "+temp[2] );
if (x.getTime() > (new Date().getTime())) {
...
}

Update this line:
// Get current date and time
var today = new Date();
// strip time to compare to the parse date
if (x.getTime() > new Date(today.getFullYear(), today.getMonth(), today.getDate()).getTime()) {
// this date has not happened yet.
alertstring = alertstring + '\n\nDEBUG CODE: 1 ' + x + '\n\n';
}

Try to put in constructor the number of month
Instead of string .
Instead of June put 6.