JavaScript 面试题 - 大数相加

function addFn(a, b) {
var lenA = a.length
var lenB = b.length
var len = lenA > lenB ? lenA : lenB
if (lenA > lenB) {
for (var i = 0; i < lenA - lenB; i++) {
b = '0' + b
}
} else {
for (var i = 0; i < lenB - lenA; i++) {
a = '0' + a
}
}
var arrA = a.split('').reverse()
var arrB = b.split('').reverse()
var arr = []
for (i = 0; i < len; i++) {
arr.push(parseInt(arrA[i]) + parseInt(arrB[i]))
}

for (i = 0; i < arr.length; i++) {
if (arr[i] >= 10) {
arr[i] -= 10
arr[i + 1] = parseInt(arr[i + 1]) + 1
}
}

return arr.reverse().join('')
}

console.log(addFn('1234599999999999999999999999999999', '66666666'))