如何从数组中减去数字以使总数为 0。我想跳过会使总数为负数的数字

Question

I am not done with this project, but I am stuck in one part of the project. I am having trouble just pushing the numbers that will make my total 0. For example if the change I need to give back is 5.50 my array should be [5,.50]. My numbers in my Array should not exceed the numbers inside myArr1. I might not be phrasing the question right but any insight on how to tackle this problem would be wonderful. Thank you!

 function checkCashRegister(price, cash, cid) { let myArr = []; let myChange = 0 let change = cash-price; let total = cash - price let myArr2 = [] let myMon = [["PENNY", .01], ["NICKEL", .05], ["DIME",.1, ],["QUARTER", .25], ["ONE", 1],["FIVE", 5],["TEN", 10],[ "TWENTY", 20],["ONE HUNDRED", 100]] let myArr1 = {"PENNY":1.01, "NICKEL": 2.05,"DIME":3.1,"QUARTER": 4.25, "ONE": 90,"FIVE": 55,"TEN": 20, "TWENTY": 60,"ONE HUNDRED": 100} let myNum = {"PENNY":.01, "NICKEL": .05,"DIME":.1,"QUARTER": .25, "ONE": 1,"FIVE": 5,"TEN": 10, "TWENTY": 20,"ONE HUNDRED": 100} for(let i =0; i <myMon.length; i++){ if(myMon[i][1] <= change){ myArr.unshift(myMon[i][1]) } } for(let i = 0; i<myArr.length; i++){ myArr2.push(total -= myArr[i]) } return myArr2 } console.log(checkCashRegister(70, 100, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]));

Answer 1

Don't work with fractions for currency. Javascript's Number type is binary-based floating point only, which means some decimal fractions aren't exactly represented. See below:

 //working with fractions of Dollars let change = 6.30 let dime = 0.10 let dimeCoins = change / dime //you won't get exactly 63 dimes console.log(63, dimeCoins, 63 - dimeCoins) //working with cents (no inexact rounding of fractional values) change = 630 dime = 10 dimeCoins = change / dime console.log(63, dimeCoins, 63 - dimeCoins)

As for your problem model, keep in mind that for every currency denomination , the cash register has a number of units with the corresponding individual value .

When picking change, the cashier always tries to exhaust the greatest bills before moving on to the lesser, next greatest ones .

You can solve this problem using no objects, two arrays and a for loop.