10/3 will give you 3.333333..., never four... if you want to check is a number will give you "whole numbers" as you say, use modulo (%).
Modulo finds the remainder of division of one number by another.
For example
10%5 = 0
because 10 divided by 5 is a "whole number"
10%3 = 1
because the closest 10/3 is 3... 3x3=9... 10-9=1
So in your code, if you want to know if a number divided by another number is whole, you need to do
if (number1%number2 == 0) { ... }
Read more about it here
EDIT :
I read your question again and I think this fiddle is what you want
var number1 = 10,
number2 = 3;
if (number1 / number2 == 0) {
alert('the numbers are whole');
} else {
var remainder = number1%number2;
var wholes = Math.floor(number1 / number2);
var output = '';
for (var i = 0; i < (wholes - 1); i++) {
output+= number2 + ', ';
}
output += (number2 + remainder);
alert(output);
}