atomic-blonde-mc.js

// Pick any four digit number and do the following:
// Rearrange the string of digits to form the largest and smallest 4-digit numbers possible.
// Take these two numbers and subtract the smaller number from the larger. 
// Suppose we choose the number 8082.
// 8820−0288=8532
// 8532−2358=6174
// 7641−1467=6174 
// It hits 6174 and then stops.
// Count also how many iterations loops are required to get to this point.
// Bonus points for recognising what 6174 is.

function fourNumSort(num) {
    const numStrArr = num.toString()
    const numArr = numStrArr.split("").map(function(element) {
        return parseInt(element)
    })
    let result
    let counter = 0
    let smallest = numArr.sort().join("")
    console.log(smallest)
    let smallestNum = parseInt(smallest)
    let largest = numArr.sort().reverse().join("")
    console.log(largest)
    let largestNum = parseInt(largest)
    while (result !== 6174) {
        result = largestNum - smallestNum
        largestNum = result.toString().split("").sort().reverse().join("")
        smallestNum = result.toString().split("").sort().join("")
        counter++
    }
    return counter
}

console.log(fourNumSort(3087))