Javascript date delta conversion to and from string

Question

I am trying to extract year, month and days data from the string 1 year, 5 months and 4 days.

Similarly, I want to be able to convert 1/2/4 into 1 year, 2 months and 4 days

In both case, I would like to handle day vs days or remove days if they are 0.

What is the best way to do this?

Read about javascript regular expression functions, i.e. String.match(). — Femi
– Femi, Commented Nov 11, 2015 at 5:38

Pranav C Balan · Accepted Answer · 2015-11-11 06:57:52Z

2

You can use replace() with callback

function format(str) {
  return str.replace(/(\d+)\/(\d+)\/(\d+)/, function(m, m1, m2, m3) {
    var s = [];
    if (m1 != 0)
      s.push(m1 + (m1 == 1 ? ' year' : ' years'));
    if (m2 != 0)
      s.push(m2 + (m2 == 1 ? ' month' : ' months'))
    if (m3 != 0)
      s.push(m3 + (m3 == 1 ? ' day' : ' days'))
    if (s.length == 3)
      return s[0] + ', ' + s[1] + ' and ' + s[2];
    else if (s.length == 2)
      return s[0] + ' and ' + s[1];
    else
      return s[0];
  })
}
document.write(format('1/2/4') +
  '<br>' + format('1/2/0') +
  '<br>' + format('0/2/0') +
  '<br>' + format('1/2/4') +
  '<br>' + format('2/2/4') +
  '<br>' + format('1/21/0') +
  '<br>' + format('0/2/1') +
  '<br>' + format('1/1/1'));

Regex explanation here

Regular expression visualization

UPDATE : Reverse can be done as following using replace() and join()

function formatRev(str) {
  return str.replace(/^(?:(\d+)\s+(\w+)\s*,\s*)?(\d+)\s+(\w+)(?:\s+and\s+(\d+)\s+(\w+))?$/ig, function(m, m1, m2, m3, m4, m5, m6) {
    var s = [0, 0, 0];
    s[extract(m2)] = m1;
    s[extract(m4)] = m3;
    s[extract(m6)] = m5;
    return s.join('/');
  })
}

function extract(str) {
  if (/year/.test(str))
    return 0;
  else if (/month/.test(str))
    return 1;
  else if (/day/.test(str))
    return 2;
  else
    return null;
}

document.write(formatRev('5 years and 4 days') +
  '<br>' + formatRev('1 year and 2 months') +
  '<br>' + formatRev('2 months') +
  '<br>' + formatRev('1 year, 2 months and 4 days')
);

Regex explanation here

Regular expression visualization

edited Nov 11, 2015 at 6:57

answered Nov 11, 2015 at 5:45

Pranav C Balan

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2 Comments

sudshekhar Over a year ago

Thanks :D What's the best way to extract it in reverse? Eg: 1 year and 3 days. I am currently using split and lots of if-else , anything more elegant you can suggest?

Tushar Over a year ago

@SudhanshuShekhar Try (?:(\d+) years?)?\s*(?:(\d+) months?)?\s*(?:(\d+) days?)? Not sure if this will help.

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