function replace_digit_in_number(number, d1, d2) {
var result = 0, multiply = 1;
while (number != 0) {
var reminder = number % 10;
if (reminder == d1)
result += d2 * multiply;
else
result += reminder * multiply;
multiply *= 10;
number = Math.trunc(number / 10);
}
return result;
}
var number = 18803808;
document.write(replace_digit_in_number(number, 8, 7));
/*
run:
17703707
*/