Multidimensional Array: Sum Numerical Values With Same String Value

Question

I am building a JavaScript cash register that returns change depending on what is in the cash register. This is for a freeCodeCamp challenge: https://www.freecodecamp.org/challenges/exact-change

Unfortunately I am close but stuck.

I have a function called addResult() which takes two arguments, name and val .

var result = [];
function addResult(name, val){
    result.push([name, val]);
}

So if the change required is $18 then the function will build an array like this.

[["ONE", 1.00], ["ONE", 1.00], ["ONE", 1.00], ["FIVE", 5.00], ["TEN", 10.00]]

I want the function to build it like this instead:

[["ONE", 3.00], ["FIVE", 5.00], ["TEN", 10.00]]

So I need to have unique string names but sum up the numbers but I can't work out how.

If anyone is interested in the full code, here it is:

 function checkCashRegister(price, cash, cid) { var totalCash = Math.round(calculateTotalCash()).toFixed(2); var changeDue = (cash - price) * 100; // 50 var result = []; var monies = [ {name: 'PENNY', val: 1}, {name: 'NICKEL', val: 5}, {name: 'DIME', val: 10}, {name: 'QUARTER', val: 25}, {name: 'ONE', val: 100}, {name: 'FIVE', val: 500}, {name: 'TEN', val: 1000}, {name: 'TWENTY', val: 2000}, {name: 'ONE HUNDRED', val: 10000} ]; function calculateTotalCash(){ var result = 0; for (var i = 0; i < cid.length; i++) { result = result + cid[i][1]; } return result; } function getQuantity(name){ for (var i = 0; i < cid.length; i++) { if (cid[i][0] == name) { return ((cid[i][1]) * 100) / monies[i].val; } } }; function addResult(name, val){ result.push([name, val]); } var changeCount = changeDue; // 50 var i = monies.length - 1; // 8 var result = []; while (changeCount > 0 && i > 0) { // get the number of currencies left in the drawer var quantity = getQuantity(monies[i].name); // console.log(quantity, monies[i].name); // alert(i); // if the currency is smaller then the change left and there are currencies left if (monies[i].val <= changeCount && quantity > 0) { // subtract the currency from the change changeCount = changeCount - monies[i].val; // and withdraw the money from the drawer cid[i][1] = ((cid[i][1] * 100) - monies[i].val) / 100; addResult(monies[i].name, monies[i].val); } else { // move on to the next smallest currency and try again i--; } } console.log(result); if (changeCount > 0) { return } // console.log(changeCount / 100); return changeCount; } // Example cash-in-drawer array: // [["PENNY", 1.01], // ["NICKEL", 2.05], // ["DIME", 3.10], // ["QUARTER", 4.25], // ["ONE", 90.00], // ["FIVE", 55.00], // ["TEN", 20.00], // ["TWENTY", 60.00], // ["ONE HUNDRED", 100.00]] checkCashRegister(19.50, 20.00, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.10], ["QUARTER", 4.25], ["ONE", 90.00], ["FIVE", 55.00], ["TEN", 20.00], ["TWENTY", 60.00], ["ONE HUNDRED", 100.00]]); // get the change due // loop through the change // check if the highest monie is greater than the change // if it is move on to the next lowest // when you find one that is lesser than the change subtract it from the change // if there is still leftover change required try and subtract again // check if it is higher than the change // do this untill the exact change is matched 

Answer 1

An easy fix would be to change the addResult function to check if the given name exists already, and if so, add the value to it

function addResult(name, val){
    let m = result.find(e => e[0] === name);
    if (m) {
        m[1] += val;
    } else {
        result.push([name, val]);
    }
}

 let result = [ ["ONE", 1.00], ["FIVE", 5.00], ["TEN", 10.00] ]; function addResult(name, val) { let m = result.find(e => e[0] === name); if (m) { m[1] += val; } else { result.push([name, val]); } } addResult("ONE", 1); console.log(result); 

Answer 2

A different way for sum cash :

 function SumCash(current,add) { var holder = {}; current.forEach(function (d) { if(holder.hasOwnProperty(d.name)) { holder[d.name] = holder[d.name] + d.value; } else { holder[d.name] = d.value; } }); add.forEach(function (d) { if(holder.hasOwnProperty(d.name)) { holder[d.name] = holder[d.name] + d.value; } else { holder[d.name] = d.value; } }); var obj2 = []; for(var prop in holder) { obj2.push({name: prop, value: holder[prop]}); } console.log(obj2); return obj2; } var current = [ {name: 'PENNY', value: 1}, {name: 'NICKEL', value: 5}, {name: 'DIME', value: 10}, {name: 'QUARTER', value: 25}, {name: 'ONE', value: 100}, {name: 'FIVE', value: 500}, {name: 'TEN', value: 1000}, {name: 'TWENTY', value: 2000}, {name: 'ONE HUNDRED', value: 10000} ]; var add = [ {name: 'PENNY', value: 1}, {name: 'NICKEL', value: 5}, {name: 'DIME', value: 10}, ]; SumCash(current,add);