Format input from M/D/YYYY to YYYYMMDD

Question

Write a function that converts user entered date formatted as M/D/YYYY to a format required by an API (YYYYMMDD). The parameter "userDate" and the return value are strings.

For example, it should convert user entered date "12/31/2014" to "20141231" suitable for the API.

function formatDate(userDate) 
{
     userDate = new Date();
     y = userDate.getFullYear();
     m = userDate.getMonth();
     d = userDate.getDate();

     return y + m + d;
}

is there anything wrong with my code?

couldn't pass an online test.

Answer 1

There are five problems with the code.

• It ignores the input parameter and uses the current time instead (Date()).
• It assumes that the computer where it runs uses the m/d/y date format to parse the string (if it actually would have parsed the string).
• The getMonth method returns the month index, not the month number, so you have to add one to it.
• It uses addition to put the values together instead of string concatenation.
• It doesn't format the month and date into two digits.

Ignoring the date format issue, the others can be fixed using:

function formatDate(userDate) {
  userDate = new Date(userDate);
  y = userDate.getFullYear().toString();
  m = (userDate.getMonth() + 1).toString();
  d = userDate.getDate().toString();
  if (m.length == 1) m = '0' + m;
  if (d.length == 1) d = '0' + d;
  return y + m + d;
}

Instead of parsing the string to a date, and the format it to a string again, you can just rearrange the characters in the string. This circumvents the date format issue:

function formatDate(userDate) {
  var parts = userDate.split('/');
  if (parts[0].length == 1) parts[0] = '0' + parts[0];
  if (parts[1].length == 1) parts[1] = '0' + parts[1];
  return parts[2] + parts[0] + parts[1];
}

Answer 2

Follow through the comments in code - step by step showing one way of solving your problem.

// Function shell. Accepts a parameter userDate, returns a value
function formatDate(userDate) {
    // Step 1: attempt to convert parameter to a date!
    var returnDate = new Date(userDate);
    
    // Step 2: now that this is a date, we can grab the day, month and year
    // portions with ease!
    var y = returnDate.getFullYear();
    var m = returnDate.getMonth() + 1; // Step 6
    var d = returnDate.getDate();
    
    // Step 3: The bit we did above returned integer values. Because we are
    // *formatting*, we should really use strings
    y = y.toString();
    m = m.toString();
    d = d.toString();

    // Step 4: The value of our month and day variables can be either 1 or 2
    // digits long. We need to force them to always be 2 digits.
    // There are lots of ways to achieve this. Here's just one option:
    if (m.length == 1) {
        m = '0' + m;
    }
    if (d.length == 1) {
        d = '0' + d;
    }

    // Step 5: combine our new string values back together!
    returnDate = y + m + d;
    
    // Step 6: did you notice a problem with the output value?
    // The month is wrong! This is because getMonth() returns a value
    // between 0 and 11 i.e. it is offset by 1 each time!
    // Look back up at Step 2 and see the extra piece of code
    
    // Step 7: Looks pretty good, huh? Well, it might pass you your quiz
    // question, but it's still not perfect.
    // Do you know why?
    // Well, it assumes that the parameter value is
    //    a) always an actual date (e.g. not "dave")
    //    b) our Step1 correctly converts the value (e.g. the client, where
    //       the JS is run, uses the date format m/d/y).
    //       I am in the UK, which doesn't like m/d/y, so my results will
    //       be different to yours!
    // I'm not going to solve this here, but is more food for thought for you.
    // Consider it extra credit!
    
    return returnDate;
}

// Display result on page -->
document.getElementById("result").innerText += formatDate("1/1/2015");

<div id="result">Result: </div>

Answer 3

function formatDate(userDate) {
  // format from M/D/YYYY to YYYYMMDD
    let array = userDate.split("/");
    while(array[0].length < 2) {
        array[0] = "0" + array[0];
    }
    while(array[1].length < 2) {
        array[1] = "0" + array[1];
    }
    let arrayAnswer = array[2]+ array[0]+ array[1];
    return arrayAnswer;
} 

console.log(formatDate("1/3/2014"));
//output must equal 20140103

As a beginner, this was the simplest way I was able to do this one. It made more sense to me to split it up, add the 0's and then sort it into the correct places.

Answer 4

 // format from M/D/YYYY to YYYYMMDD

function formatDate(userDate) {
  var dateObj = new Date(userDate);
  let year = dateObj.getFullYear();  
  let date = ('0' + (dateObj.getDate())).slice(-2);
  let month = ("0" + (dateObj.getMonth() + 1)).slice(-2);
  return '' + year + month + date;
}

console.log("The converted date is : " , formatDate("12/31/2014"));

Answer 5

You are using + with integers, you have to cast them as string.

function formatDate(userDate) {
  userDate = new Date(userDate);

  y = userDate.getFullYear();
  m = userDate.getMonth() + 1;
  d = userDate.getDate();

  return y.toString() +
         ('0' + m.toString()).slice(-2) +
         ('0' + d.toString()).slice(-2);
}

And also you need to add leading zero to month and day.

Example:

console.log(formatDate('2/12/2015'));

will write to log 20150212

console.log(formatDate('1/1/2015'));

will write to log 20150101

Answer 6

function formatDate(userDate) {
    var first  = userDate.indexOf("/");
    var last   = userDate.lastIndexOf("/");
    var months = userDate.substring(0, first);
    var years  = userDate.substring(last + 1);
    var days   = userDate.substring(last, 3);
    return (years + months + days);
}

console.log(formatDate("12/31/2014"));

Answer 7

function formatDate(userDate) {
  let userdate = userDate.split('/');

  let [month, day, year] = userdate;

  if (day.length === 1) {
    day = `0${day}`;
  }

  if (month.length === 1) {
    month = `0${month}`;
  }

  return `${year}${month}${day}`;

}

console.log(formatDate("12/1/2014"));

Answer 8

function formatDate(userDate) {
    const month = userDate.substr(0, 2)
    const day = userDate.substr(3, 2)
    const year = userDate.substr(6)
    return year + month + day
}
console.log(formatDate("12/31/2014"));

Answer 9

function formatDate(userDate) {
  // format from M/D/YYYY to YYYYMMDD
  let [month,date,year] = userDate.split("/");
  month = (month.length === 1) ? "0"+month : month;
  date = (date.length === 1) ? "0"+date : date;
  
  return year+month+date
}

console.log(formatDate("1/31/2014"));

Answer 10

function formatDate(userDate) {
// receiving m/d/yyyy
  let userdate = userDate.split("/");
if(userdate[0].length == 1){userdate[0]='0'+userdate[0];}
if(userdate[1].length == 1){userdate[1]='0'+userdate[1];}
let temp = userdate[0];
userdate[0]=userdate[2];
userdate[2]=userdate[1];
userdate[1]=temp;
  temp = userdate.join("");
  return temp;
}
document.write("Our format = 12/31/2018");
document.write("<br />");
document.write("received format ="+formatDate("12/31/2018"));
document.write("<hr />");
document.write("Our format = 2/1/2018");
document.write("<br />");
document.write("received format ="+formatDate("2/1/2018"));

Answer 11

function formatDate(userDate) {
  // format from M/D/YYYY to YYYYMMDD
  var oldDate = String(userDate).split('/');
  if (oldDate[0].length==1)oldDate[0]='0'+oldDate[0];
  if (oldDate[1].length==1)oldDate[1]='0'+oldDate[1];
  var newDate = [oldDate[2], oldDate[0], oldDate[1]];
  return newDate.join('');
}

console.log(formatDate("12/31/2014"));

Answer 12

function formatDate(userDate) {
  userDate = new Date(userDate);
  year= userDate.getFullYear().toString();
  month = (userDate.getMonth() + 1).toString();
  date = userDate.getDate().toString();

  return year + (month=(month.length==1)?'0'+month:month) + (date=(date.length==1)?'0'+date:date);
}

console.log(formatDate("12/10/2017"));

Some more details:

(1)userDate = new Date(userDate) => create an instance of Date object.

(2)userDate.getFullYear() is get year from userDate. Similarly user.getMonth() for month and userDate.getDate() for date...I've added +1 to month because month return is starts 0, i.e for month 6 it return 5 so 1 is added.

(3) in return statement year+month+date is done where there is tenary condition to check if month or date is single digit like 1 or 3 then 0 is added before it to make it 01 or 03.