How do I use map reduce to total the 2nd property of an array

[TurtleWolf1]

This is an early step in the Cash Register Challenge at Free Code Camp, I think I’ve got ahead of the curriculm a bit, but I was also hoping most of it would be review. I thought I could start preplanning my projects with psuedo code.
I’m just trying to make a variable that would take the 2nd property of the array and sum a total to represent how much is in the drawer at the moment

let cid = [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]
var totalINdrawer = [cid]; //reduce the 2nd property of an arrary

var myData = reduce.cid[i][1];
console.log(myData);

[Paul_Wilkins]

It is an array of arrays, where the main array contains currency and the inner array is the name and amount.

To gain a total, you can use reduce to achieve that, and before that use map to get just the amounts.

var total = cid.map(currency => currency[1])
    .reduce((total, amount) => total + amount);

[TurtleWolf1]

…that returns $335.40999999999997? The cents should add up to .41 I guess it’s some sort of rounding error since we’re already operating behind the decimal. Should I just round it up? Or should I try to correct for it somewhere sooner in the process? I’d like to understand more about where the anomaly starts… If I started by multiplying them all by 100 then divided afterwords, would that correct for it? Or is that most likely what it’s already doing and where the anomaly starts at?

[TurtleWolf1]

Avoiding Problems with Decimal Math in JavaScript

This link implies I was on the correct path. I should probably multiply all the cents by 100 to be working with whole numbers, I should probably do that in the mapping phase before the reduction takes place.

[TurtleWolf1]

let cid = [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]
var total = cid.map(currency => currency[1]*100)
    .reduce((total, amount) => total + amount);
console.log(total);
total = total/100;
console.log(total);

ok, this is getting me the number I was hoping for, thank you for pointing me in the right direction

[WolfShade]

Or, you could do it the first way and round it using .toFixed(2).

Just my two cents.

V/r,

^ _ ^