時間と分の形式で浮動小数点数を合計するにはどうすればよいですか？

var arr = [0.15, 0.2, 3.45, 0.4, 2, 0.3, 5.2, 1, 1.4, 1.1, 2.4, 1, 3.4]
    
var sum = 0.0;
    
arr.forEach(function(item) {
  console.log(sum);
  sum += parseFloat(item);
});

// converts a pseudo-float of the form hh.mm into an integer number of minutes
// robust against floating-point roundoff errors, also works for negative numbers
function hhMmToMinutes(x) {
  const hhmm = Math.round(100 * x)  // convert hh.mm -> hhmm
  return 60 * Math.trunc(hhmm / 100) + (hhmm % 100)
}

// convert minutes back to hh.mm pseudo-float format
// use minutesToHhMm(minutes).toFixed(2) if you want trailing zeros
function minutesToHhMm(minutes) {
  return Math.trunc(minutes / 60) + (minutes % 60) / 100
}

const arr = [0.15, 0.2, 3.45, 0.4, 2, 0.3, 5.2, 1, 1.4, 1.1, 2.4, 1, 3.4]

let sum = 0
console.log( arr.map(hhMmToMinutes).map(x => sum += x).map(minutesToHhMm) )

console.log(Math.trunc(100 * 0.29))  // you'd think this would be 29...

// We got this after simple addition
// Now we want to change it into 4.2
sample = 3.8

// Now here are the minutes that the float currently shows
minutes = (sample % 1) * 100

// And the hours
hours = Math.floor(sample)

// Here are the number of hours that can be reduced from minutes
AddHours = Math.floor(minutes / 60)

// Adding them to the hours count
hours += AddHours

// Reducing mintues
minutes %= 60

// Finally formatting hour and minutes into your format
final = hours + (minutes / 100.0)
console.log(final)

const resultObj = [0.35, 3.45].reduce((a, e) => {
  const [hours, minutes] = e.toString().split('.');
  a.h += +hours;
  a.m += (+(minutes.padEnd(2, 0)) || 0); 
  return a;
}, {h: 0, m: 0});


const result = resultObj.h + Math.floor(resultObj.m / 60) + ((resultObj.m % 60) / 100);
console.log(result);

var arr = [0.15, 0.2, 3.45, 0.4, 2, 0.3, 5.2, 1, 1.4, 1.1, 2.4, 1, 3.4];

function add(arr) {
  var hm = arr
    .map(v => [Math.floor(v), (v % 1).toFixed(2) * 100])  // Map the array to values having [hours, minutes]
    .reduce((t, v) => { //  reduce the array of [h, m] to a single object having total hours and minutes
      t = {
        h: t.h + v[0],
        m: t.m + v[1]
      };
      return t;
    }, {
      h: 0,
      m: 0
    });

  // final result would be = 
  // total hours from above
  // + hours from total minutes (retrived using Math.floor(hm.m / 60)) 
  // + minutes (after converting it to be a decimal part)
  return (parseFloat(hm.h + Math.floor(hm.m / 60)) + parseFloat(((hm.m % 60) / 100).toFixed(2))).toFixed(2);
}

// adding `arr` array
console.log(add(arr));

// adding 0.35+3.45
console.log(add([0.35, 3.45]));

var arr = [0.15, 0.2, 3.45, 0.4, 2, 0.3, 5.2, 1, 1.4, 1.1, 2.4, 1, 3.4];
let hoursTally = 0;
let minutesTally = 0;

for(var i = 0; i < arr.length; i++) {
  // Convert the float to a string, as floats can be a pain to add together
  let time = arr[i].toString().split('.');
  // Tally up the hours.
  hoursTally += parseInt(time[0]);
  // Tally up the minutes;
  let minute = time[1];
  if(minute) {
    // We do this so we add 20 minutes, not 2 minutes
    if(minute.length < 2) {
      minutesTally += parseInt(minute) * 10;
    } else {
      minutesTally += parseInt(minute);
    }
    // If the minutesTally is greater than 60, add an hour to hours
    if(minutesTally >= 60) {
      hoursTally++;
      // Set the minutesTally to be the remainder after dividing by 60
      minutesTally = minutesTally % 60;
    }
  }
  console.log(hoursTally + "." + minutesTally);
}

const arr = [0.15, 0.2, 3.45, 0.4, 2, 0.3, 5.2, 1, 1.4, 1.1, 2.4, 1, 3.4]

const reducer = (acc, curr) => {
  acc = `${acc}`.split('.').length > 1 ? acc : `${acc}.0`;
  curr = `${curr}`.split('.').length > 1 ? curr : `${curr}.0`;
  let hours = parseStrAndSum(true, `${acc}`.split('.')[0], `${curr}`.split('.')[0]);
  let minute = parseStrAndSum(false, `${acc}`.split('.')[1], `${curr}`.split('.')[1]);
  hours = parseInt(hours / 1) + parseInt(minute / 60);
  minute = minute % 60;
  console.log(`${acc} + ${curr} = ${hours}.${minute}`);
  return `${hours}.${minute}`;
}

const parseStrAndSum = (is_hours, ...strs) => {
  let result = 0;
  strs.forEach(function(number) {
    if (!is_hours) {
      number = number.length == 1 ? `${number}0` : number;
    }
    result += parseInt(number);
  });
  return result;
};

arr.reduce(reducer);