open

change2.js

var tender = {1: "PENNY", "PENNY": 1, 5: "NICKEL","NICKEL": 5, 10: "DIME", "DIME": 10, 25: "QUARTER", "QUARTER": 25,
              100: "ONE","ONE": 100, 500: "FIVE", "FIVE": 500, 1000: "TEN", "TEN": 1000, 2000: "TWENTY", 
              "TWENTY": 2000, a10000: "ONE HUNDRED", "ONE HUNDRED": 10000};

function numberOfTender(value,cid,possibleChange){
  var maxTender = possibleChange.filter(function(x){return x<=value;}).pop();
  var maxNumTender = Math.floor(value/maxTender);
  var tenderAvailable = cid.map(function(n){if (n[0] == tender[maxTender]) return n[1];})
                           .filter(notUndefined)
                           .map(Number) / (maxTender/100) || 0;
  return [maxTender,Math.min(maxNumTender,tenderAvailable)];
}

function notUndefined(n){return n !== undefined;}
function monetize(n){return n * 100;}
function secondColumn(value){return value[1];}
function sum(x,y){return x + y;}

function drawer(price, cash, cid) {
  price = price * 100;
  cash = cash * 100;
  var change = cash - price;  
  var till = cid.map(secondColumn).map(monetize).reduce(sum); 
  if (change == till) return "Closed";
  return formatChange(makeChange(change,cid)) || "Insufficient Funds";
}

function makeChange(remaining,cid){//returns an array consisting of [value of tender,number of coins]
  var possibleChange = cid.map(function(value,index) { return value[0]; }).map(function(name){return tender[name];});
  result = [];
  while (remaining > 0){
    var tenderInfo = numberOfTender(remaining,cid,possibleChange);
    result.push(tenderInfo);
    remaining -= (tenderInfo[0] * tenderInfo[1]);
    var ndx = possibleChange.indexOf(tenderInfo[0]);
    if (ndx == -1)//we have run out of change to use without finishing
      return false;
    possibleChange = possibleChange.slice(0,ndx);
  }
  return result;
}

function formatChange(arr){//returns an array consisting of [tender name,value]
   for(var i=0;i<arr.length;i++){
    var coinName = tender[arr[i][0]];
    var coinValue = arr[i][0] / 100 * arr[i][1];
    arr[i] = [coinName,coinValue];    
  }
  return arr;
}