hacktive8.js

// Second Great Low
function secondGreatLow(arr) {
  let result = [];
  let sortedArr = arr.sort((a,b) => a-b);
  // turn into Set data structure first, then convert it again to array
  sortedArr = [...new Set(sortedArr)];
  
  const length = sortedArr.length;
  
  // need more info on how many numbers minimum that must be returned
  if (length == 2) {
    result.push(sortedArr[length-2])
  } else {
    result.push(sortedArr[1])
    result.push(sortedArr[length-2])    
  }

  return result.join(' ');
}

// Multiplicative Persistence

function MultiplicativePersistence(num) {
      let count = 0;
      let currentNum = num;
    
       function multiply(arr){
          const result = arr.reduce((a,b) => a*b);
          return result;
       }
       
       while(currentNum.toString().length > 1) {
           let tempNum = currentNum.toString().split("");
           currentNum = multiply(tempNum);
           count +=1;
        }
        return count;
    }

// Mean Mode

function MeanMode(arr) {
    let result = 0;
    const meanValue = parseInt(mean(arr));
    const modeValue = parseInt(mode(arr));
  
    if (meanValue === modeValue) {
      result = 1;
    }

    function mean(numbers) {
        let total = 0,
            i;
        for (i = 0; i < numbers.length; i += 1) {
            total += numbers[i];
        }
        return total / numbers.length;
    }

    function mode(numbers) {
        let modes = [],
            count = [],
            i, number, maxIndex = 0;

        for (i = 0; i < numbers.length; i += 1) {
            number = numbers[i];
            count[number] = (count[number] || 0) + 1;
            if (count[number] > maxIndex) {
                maxIndex = count[number];
            }
        }

        for (i in count)
            if (count.hasOwnProperty(i)) {
                if (count[i] === maxIndex) {
                    modes.push(Number(i));
                }
            }

        return modes;
    }
    
    return result;
}


console.log("== Second Great Low ==")
const testArr = [7,7,12,98,106]
const testArr2 = [7,12]
secondGreatLow(testArr)
secondGreatLow(testArr2)

console.log("== Multiplicative Persistence ==")
MultiplicativePersistence(39)
MultiplicativePersistence(12)

console.log("== Mean Mode ==")
MeanMode([1,2,3,3]);
MeanMode([5,3,3,3,1]);