Calculate age from date and month only JS-CodePudding

dob format is 2022-07

desired output is 0 Years 5 Months

Below is the code I tried but I am getting months in negative.

export default function calculateAge(date) {
  let month = new Date().getMonth() - Number(date.split("-")[1]);
  let year = new Date().getFullYear() - Number(date.split("-")[0]);
  console.log(`month is`, month);

  if (month < 0 && year < 1) {
    month = year * 12   month;
    year = 0;
  }

  console.log(`year`, year);

  return `${year ? `${year} Year${year > 1 ? `s` : ""}` : ""} ${
    month ? `${month} Month${month > 1 ? "s" : ""}` : ""
  }`;
}

CodePudding user response：

function calculateAge(date) {
  const now = new Date()
  const then = new Date(...date.split('-'))

  const diff = new Date(now - then)
  const months = diff.getMonth()
  const years = diff.getUTCFullYear() - 1970

  return `${years} ${years !== 1 ? 'Years' : 'Year'} ${months} ${months !== 1 ? 'Months' : 'Month'}`
}

const age = calculateAge('2010-05')
console.log(age)

CodePudding user response：

function calculateAge(date) {
  // Split the date string into year and month
  const [year, month] = date.split("-");

  // Get the current year and month
  const currentYear = new Date().getFullYear();
  const currentMonth = new Date().getMonth()   1; // months are 0-indexed in JavaScript

  // Calculate the difference in years and months
  let ageYears = currentYear - Number(year);
  let ageMonths = currentMonth - Number(month);

  // If the age in months is negative, subtract 1 from the age in years and add 12 to the age in months
  if (ageMonths < 0) {
    ageYears -= 1;
    ageMonths  = 12;
  }

  // Return the age in years and months as a string
  return `${ageYears ? `${ageYears} Year${ageYears > 1 ? `s` : ""}` : ""} ${
    ageMonths ? `${ageMonths} Month${ageMonths > 1 ? "s" : ""}` : ""
  }`;
}

CodePudding user response：

You are missing the "modulo" exprerience Remainder (%)

and calculate the difference in number of months (1 year = 12 months)
then convert the result to years / months

as none of the previous answers seem correct to me...

function calculateAge( start_date, end_Date )  // end_Date is optionnal
  {
  const
    [ yRef, mRef ] = start_date.split('-').map(Number)
  , today          = new Date()
  , [ yEnd, mEnd ] = !!end_Date 
                   ? end_Date.split('-').map(Number)
                   : [ today.getFullYear(), today.getMonth()  1 ]
  , delta_Months   = ((yEnd - yRef) * 12)   mEnd -mRef 
  , months         = delta_Months % 12
  , years          = (delta_Months - months) / 12
    ;
  return `${years} Year(s), ${months} Month(s)`
  }

I also added more examples so that everyone can check the correctness of the result.

// actual date on code writing is  2022-12
// PO test values . . . . . . .  = 2022-07  
// PO expected return . . . . .  = 0 Years 5 Months
 
console.log(calculateAge('2022-07'))  // 0 Year(s), 5 Month(s)

console.log(('--- -- - --- -- - --- -- - other tests'))
console.log(calculateAge('2010-05'))   // 12 Year(s), 7 Month(s)
console.log(calculateAge('2010-10'))   // 12 Year(s), 2 Month(s)
console.log(calculateAge('2010-11'))
console.log(calculateAge('2010-12'))   // 12 Year(s), 0 Month(s)
console.log(calculateAge('2011-01'))
console.log(calculateAge('2011-02'))   // 11 Year(s), 10 Month(s)

console.log(('--- -- - --- -- - --- -- - test with specifics ending date '))
console.log(calculateAge('2020-01','2022-06'))  // 2 Year(s), 5 Month(s)
console.log(calculateAge('2020-06','2022-06'))  // 2 Year(s), 0 Month(s)
console.log(calculateAge('2020-06','2022-01'))  // 1 Year(s), 7 Month(s)

function calculateAge( start_date, end_Date )  // end_Date is optionnal
  {
  const
    [ yRef, mRef ] = start_date.split('-').map(Number)
  , today          = new Date()
  , [ yEnd, mEnd ] = !!end_Date 
                   ? end_Date.split('-').map(Number)
                   : [ today.getFullYear(), today.getMonth()  1 ]
  , delta_Months   = ((yEnd - yRef) * 12)   mEnd -mRef 
  , months         = delta_Months % 12
  , years          = (delta_Months - months) / 12
    ;
  return `${years} Year(s), ${months} Month(s)`
  }

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