javascript - Elegant method to generate array of random dates within two dates - Stack Overflow

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I have a datepicker where I show two months and I want to randomly choose 3 dates in each visible month

  $('.date').datepicker({
    minDate: new Date(),
    dateFormat: 'DD, MM, d, yy',
    constrainInput: true,
    beforeShowDay: processDates,
    numberOfMonths: 2,
    showButtonPanel: true,
    showOn: "button",
    buttonImage: "images/calendar_icon.jpg",
    buttonImageOnly: true    
  });

Here is my calculation

var now = new Date();
var nowTime = parseInt(now.getTime()/1000);
var randomDateSet = {};

function getRandomSet(y,m) {
  var monthIndex = "m"+y+""+m; // m20121 for Jan
  if (randomDateSet[monthIndex]) return randomDateSet[monthIndex];
  // generate here
.
. - I need this part
.
  return randomDateSet[monthIndex];
}

function processDay(date) { // this is calculated for each day so we need a singleton for the array
  var dateTime = parseInt(date.getTime()/1000);
  if (dateTime <= (nowTime-86400)) {
    return [false]; // earlier than today
  }
  var m = date.getMonth(), d = date.getDate(), y = date.getFullYear();
  var randomDates = getRandomSet(y,m);

  for (i = 0; i < randomDates.length; i++) {
    if($.inArray((m+1) + '-' + d + '-' + y,randomDates) != -1 || new Date() > date) {
      return [true,"highlight","Some message"];
    }
  }
  return [true,"normal"]; // ordinary day
}

I have a datepicker where I show two months and I want to randomly choose 3 dates in each visible month

  $('.date').datepicker({
    minDate: new Date(),
    dateFormat: 'DD, MM, d, yy',
    constrainInput: true,
    beforeShowDay: processDates,
    numberOfMonths: 2,
    showButtonPanel: true,
    showOn: "button",
    buttonImage: "images/calendar_icon.jpg",
    buttonImageOnly: true    
  });

Here is my calculation

var now = new Date();
var nowTime = parseInt(now.getTime()/1000);
var randomDateSet = {};

function getRandomSet(y,m) {
  var monthIndex = "m"+y+""+m; // m20121 for Jan
  if (randomDateSet[monthIndex]) return randomDateSet[monthIndex];
  // generate here
.
. - I need this part
.
  return randomDateSet[monthIndex];
}

function processDay(date) { // this is calculated for each day so we need a singleton for the array
  var dateTime = parseInt(date.getTime()/1000);
  if (dateTime <= (nowTime-86400)) {
    return [false]; // earlier than today
  }
  var m = date.getMonth(), d = date.getDate(), y = date.getFullYear();
  var randomDates = getRandomSet(y,m);

  for (i = 0; i < randomDates.length; i++) {
    if($.inArray((m+1) + '-' + d + '-' + y,randomDates) != -1 || new Date() > date) {
      return [true,"highlight","Some message"];
    }
  }
  return [true,"normal"]; // ordinary day
}

• javascript
• date
• random
• jquery-ui-datepicker

Share Improve this question Follow asked Jan 27, 2012 at 15:22 mplungjanmplungjan 177k2828 gold badges180180 silver badges240240 bronze badges 0

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7 Answers 7

Sorted by: Reset to default 340

Maybe I am missing something, but isn't this it?

function randomDate(start, end) {
  return new Date(start.getTime() + Math.random() * (end.getTime() - start.getTime()));
}

const d = randomDate(new Date(2012, 0, 1), new Date());
console.log(d);

console.log(
  new Date(new Date() - Math.random()*(1e+12))
)

Using Moment.js && @Demven Weir's answer to get a string value like "03/02/1975".

moment(new Date(+(new Date()) - Math.floor(Math.random()*10000000000)))
.format('MM/DD/YYYY');

NOTE: Keep adding a zero at a time to increase the span of years produced.

function generateRandomDate() {
return new Date(+(new Date()) - Math.floor(Math.random() * 10000000000));
}

(new generateRandomDate()).toLocaleDateString('en-US')

You will get a random date in US format 4/25/2021

See this Demo on jsfiddle

You can convert the boundary dates to integers (Date.getTime()) and then use Math.random() to generate your random dates within given boundaries. Then go back to Date objects with Date.setTime().

You can use this snippet to get random date and format;

const emptyDate = new Date();
const randomDate = new Date();
const dateFormatter = Intl.DateTimeFormat('sv-SE');
const formattedRandomDate = dateFormatter.format(emptyDate.setDate(randomDate.getDate() - Math.floor(Math.random()*1000)));

From examples in date-fns

const result = eachDayOfInterval({
  start: new Date(2014, 9, 6),
  end: new Date(2014, 9, 10)
})

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