mapExample.js

var dinnerBills = [
{name:'Otto',  bill: 12.45 },
{name:'Jax',   bill: 9.55  },
{name:'Chibs', bill: 15.25 },
{name:'Tig',   bill: 11.75 }
];

var taxPercent = 8.75;
var tipPercent = 15.00;

function calcEach(eachBill) {
    return ((eachBill) + 
      (eachBill / taxPercent) + 
      (eachBill / tipPercent)).toPrecision(4);
}

function getTotalBillAmount (eachBill) {
    var personalBill = {};
    personalBill['name'] = eachBill.name;
    personalBill['bill'] = calcEach(eachBill.bill);
    return personalBill;
}
 
var newDinnerBills = dinnerBills.map(getTotalBillAmount);

console.log(newDinnerBills);