Finding quarter based on month index in JavaScript

We are required to write a JavaScript function that takes in the 1-based month index and return the quarter which the month falls in.

Understanding Quarters

A year is divided into four quarters, each containing three months:

• Q1: January, February, March (months 1-3)
• Q2: April, May, June (months 4-6)
• Q3: July, August, September (months 7-9)
• Q4: October, November, December (months 10-12)

Method 1: Using if-else Statements

const month = 7;
const findQuarter = (month = 1) => {
   if (month <= 3) {
      return 1;
   } else if (month <= 6) {
      return 2;
   } else if (month <= 9) {
      return 3;
   } else if (month <= 12) {
      return 4;
   }
};

console.log("Month", month, "is in quarter:", findQuarter(month));

Month 7 is in quarter: 3

Method 2: Using Math.ceil Formula

A more concise approach uses mathematical calculation:

const findQuarterMath = (month) => {
   return Math.ceil(month / 3);
};

// Test with different months
console.log("Month 1:", findQuarterMath(1));  // Q1
console.log("Month 4:", findQuarterMath(4));  // Q2
console.log("Month 7:", findQuarterMath(7));  // Q3
console.log("Month 10:", findQuarterMath(10)); // Q4

Month 1: 1
Month 4: 2
Month 7: 3
Month 10: 4

Method 3: Using Array Lookup

const findQuarterArray = (month) => {
   const quarters = [1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4];
   return quarters[month - 1];
};

console.log("Month 5:", findQuarterArray(5));
console.log("Month 11:", findQuarterArray(11));

Month 5: 2
Month 11: 4

Complete Example with Validation

const getQuarter = (month) => {
   // Input validation
   if (month < 1 || month > 12 || !Number.isInteger(month)) {
      return "Invalid month. Please enter a number between 1-12.";
   }
   
   return Math.ceil(month / 3);
};

// Test cases
const testMonths = [1, 3, 6, 8, 12, 0, 13];
testMonths.forEach(month => {
   console.log(`Month ${month}: ${getQuarter(month)}`);
});

Month 1: 1
Month 3: 1
Month 6: 2
Month 8: 3
Month 12: 4
Month 0: Invalid month. Please enter a number between 1-12.
Month 13: Invalid month. Please enter a number between 1-12.

Comparison

Conclusion

The Math.ceil formula Math.ceil(month / 3) is the most efficient approach for finding quarters. It's concise and performs well for large datasets.