MakeChange

change.js

//For a given dollar amount (as an integer 100 == $1) compute all combinations of coins
//that can make even change

let changePermutations = (v, coinDenominations) => {

    let subCombinations = (accum, sumAccum, total, coins) => {
        //Base case: there's no coins left to try or remaining coins would take us beyond zero
        if(coins.length == 0 || total < 0) return accum;
        //This coin being attempted reduces to zero, making even change
        if(total == 0) return accum.concat([sumAccum]);
        //Recurse step: 
        //One stack trying the next denomination without removing the current one
        //Another stack removing current step's denomination from rolling total and proceeding with all denominations
        return subCombinations(accum, sumAccum, total, coins.slice(1)).concat(
            subCombinations(accum, [coins[0]].concat(sumAccum), total - coins[0], coins)
        )
    }

    return subCombinations([],[],v,coinDenominations)
}

changePermutations(100, [1,5,10,25,50,100]).forEach(x => console.log(x))