Question 161541 in Javascript Question posted in
A very good W3school tutorial can be found here.

What quarter number does Feb start in when using Javascript?

How do I get a quarter number if the quarter starts in February?

Quarter 1: Feb – April

Quarter 2: May – July

Quarter 3: August – October

Quarter 4: November – January

The following won’t work because of the overlap November – January for quarter 4. I have also tried incrementing, subtracting month or total by 1. Not sure which way I should go.

const month = 1; // January = 1

function getQuarter(month) {
  return Math.ceil(month / 3);
}

Expected result

getQuarter(1);  // 4
getQuarter(11); // 4
getQuarter(12); // 4
getQuarter(2);  // 1
getQuarter(5);  // 2
getQuarter(8);  // 3
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3

Answers


  1. 0

    You could use the remainder (%) operator to apply your offset:

    ((month + 10) % 12) + 1

    This is just a fancy way of doing an if/else based on the month were we subtract 1, unless the input is 1, then we set it to 12:

    let customMonth = (month === 1) ? 12 : (month - 1);

    So the final result, using the remainder operator, as a one-liner:

    function getQuarter(month) {
    return Math.ceil((((month + 10) % 12) + 1) / 3);
}

for (let i = 1; i <= 12; i++) {
    console.log(`${i} -> ${getQuarter(i)}`);
}
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  2. 0

    Since your first quarter start in february you need to minus 1 the month and handle the january month as a special case and just return 4

    You can also handle if invalid number given

    function getQuarter(month) {
  if (month < 1 || month > 12) return null

  if (month === 1) return 4

  return Math.ceil((month - 1) / 3);
}

console.log(getQuarter(0), null)
console.log(getQuarter(1), 4) // January
console.log(getQuarter(2), 1) // February
console.log(getQuarter(3), 1) // March
console.log(getQuarter(4), 1) // April
console.log(getQuarter(5), 2) // May
console.log(getQuarter(6), 2) // June
console.log(getQuarter(7), 2) // July
console.log(getQuarter(8), 3) // August
console.log(getQuarter(9), 3) // September
console.log(getQuarter(10), 3) // October
console.log(getQuarter(11), 4) // November
console.log(getQuarter(12), 4) // December
console.log(getQuarter(13), null)
    <pre>
Quarter 1: Feb - April

Quarter 2: May - July

Quarter 3: August - October

Quarter 4: November - January
</pre>
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  3. 0

    You can do this mathematically.

    function getQuarter(month) {
  
  // Rotate month values so that February starts at zero
  month = (month + 10) % 12;
  
  // Find the zero-based quarter: Feb to Apr => 0, May to Jun => 1, etc.
  quarter = Math.floor(month / 3);
   
  // Add 1 so that q0 to q3 is returned as q1 to q4.
  return quarter + 1;
}

for (let month = 1; month <= 12; month++)
  console.log(`Month: ${month} - Quarter: ${getQuarter(month)}`);
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