Algorithm Friendly Date Ranges

Algorithm Friendly Date Ranges

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🏁 Problem Explanation:

Create a program that will take two dates and convert them into a more easy to understand date such as January 1st, 2017. It will also check the difference between them, and handles cases with no difference, more than a day, more than a month, more than a year, and more than a month and less than a year respectively.

Relevant Links

• Global Object Date

💬 Hint: 1

Split the string into an array where you get "YYYY", "MM", "DD".

try to solve the problem now

💬 Hint: 2

You need to handle the case for "st", "nd", and "th". Note that 13 is "th" not "rd".

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💬 Hint: 3

If you are using Date() to create instances of dates to work with, then use UTC time to avoid errors due to time zone difference between servers.

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Spoiler Alert!

Solution ahead!

🔰 Basic Code Solution:

function makeFriendlyDates(str) {

  var months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];

  // Convert a YYYY-MM-DD string into a date object.
  function convertDate(str) {
    // Split the dates to work independently.
    var dateStr = str.split('-');

    // Force the dates into Universal time to avoid issues due to timezones.
    return (new Date(Date.UTC(dateStr[0], dateStr[1] - 1, dateStr[2])));

  }

  // Handles the case of the day's endings.
  function dateEnding(val) {
    switch (val) {
      case 1:
      case 21:
      case 31:
        return val + 'st';
      case 2:
      case 22:
        return val + 'nd';
      case 3:
      case 23:
        return val + 'rd';
      default:
        return val + 'th';
    }
  }

  // Checks for the real difference in months to avoid errors
  function monthDiff(date1, date2) {
    var month2 = date2.getUTCFullYear() * 12 + date2.getUTCMonth();
    var month1 = date1.getUTCFullYear() * 12 + date1.getUTCMonth();
    return month2 - month1;
  }

  //day diff
  function dayDiff(date1, date2) {
    if(date2.getUTCMonth() === date1.getUTCMonth()){
      return date1.getUTCDate()-date2.getUTCDate();
    }
    return 0;
  }

  // Get's the right month string.
  function getMonth(date) {
    return months[date.getUTCMonth()];
  }

  function displayDate() {

    // Handles same day
    if (date2.getTime() - date1.getTime() === 0) {
      return [getMonth(date1) + ' ' + dateEnding(date1.getUTCDate()) + ', ' + date1.getUTCFullYear()];
    }

    // Handles same month
    if (date1.getUTCMonth() === date2.getUTCMonth() && date1.getUTCFullYear() === date2.getUTCFullYear()) {
      return [getMonth(date1) + ' ' + dateEnding(date1.getUTCDate()), dateEnding(date2.getUTCDate())];
    }

    // Handles more than a month of difference, but less than 12 months and different year
    if (monthDiff(date1, date2) < 12 && date1.getUTCFullYear() !== date2.getUTCFullYear() ) {
      return [getMonth(date1) + ' ' + dateEnding(date1.getUTCDate()), getMonth(date2) + ' ' + dateEnding(date2.getUTCDate())];
    }

    // Handles same month but different year
    if (monthDiff(date1, date2) <= 12 && dayDiff(date1, date2)>0) {
      return [getMonth(date1) + ' ' + dateEnding(date1.getUTCDate())+', '+date1.getUTCFullYear(), getMonth(date2) + ' ' + dateEnding(date2.getUTCDate())];
    }

    // Handles more than a month of difference, but less than 12 months and same year
    if (monthDiff(date1, date2) < 12) {
      return [getMonth(date1) + ' ' + dateEnding(date1.getUTCDate())+', '+date1.getUTCFullYear(), getMonth(date2) + ' ' + dateEnding(date2.getUTCDate())];
    }

    // Handles cases with more than 12 months apart.
    return [getMonth(date1) + ' ' + dateEnding(date1.getUTCDate()) + ', ' + date1.getUTCFullYear(), getMonth(date2) + ' ' + dateEnding(date2.getUTCDate()) + ', ' + date2.getUTCFullYear()];
  }

  var date1 = convertDate(str[0]);
  var date2 = convertDate(str[1]);

  return displayDate();

}

// test here
makeFriendlyDates(['2016-07-01', '2016-07-04']);

🚀 Run Code

Code Explanation:

• The function convertDate() converts a string in the format YYYY-MM-DD to a date object.
  • split() the dates on - to work independently.
  • Force the dates into universal time to avoid timezone issues.
• The function dateEnding() handles day's ending i.e., appending st, nd, rd or th.
• The function monthDiff() checks the real difference in month to avoid errors.
• The function dayDiff() checks the real difference in day to avoid errors.
• The function getMonth() returns month string for particular date.
• The function displayDate() displays the date correctly. Following provisions are made:
  • Handles same day.
  • Handles same month.
  • Handles more than a month of difference, but less than 12 months and different year.
  • Handles same month but different year.
  • Handles more than a month of difference, but less than 12 months and same year.
  • Handles cases with more than 12 months apart.

Relevant Links

• JS String Prototype Split
• Date.UTC()
• Date.prototype.getUTCFullYear()
• Date.prototype.getUTCMonth()
• Date.prototype.getUTCDate()
• Date.prototype.getTime()

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