Algorithm Friendly Date Ranges - thelastmile/FreeCodeCamp GitHub Wiki

Algorithm Friendly Date Ranges

:triangular_flag_on_post: Remember to use Read-Search-Ask if you get stuck. Try to pair program :busts_in_silhouette: and write your own code :pencil:

:checkered_flag: 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

:speech_balloon: Hint: 1

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

try to solve the problem now

:speech_balloon: Hint: 2

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

try to solve the problem now

:speech_balloon: 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.

try to solve the problem now

Spoiler Alert!

Solution ahead!

:beginner: 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']);

:rocket: 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.

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:trophy: Credits:

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