Zyzzyzus' number shortener with full names

nums = ['thousand','million','billion','trillion','quadrillion','quintillion', 'sextillion', 'septillion', 'octillion', 'nonillion', 'decillion', 'undecillion', 'duodecillion', 'tredecillion', 'quattuordecillion', 'quindecillion', 'sexdecillion', 'septendecillion', 'octodecillion', 'novemdecillion', 'vigintillion'];


function Beautify(num,floats)
{
if (!isFinite(num)) return 'Infinity'
if(num < 1e3 || num >= parseFloat('1e' + 3*(nums.length))) return Math.round(num)
var i = 0;
while(num >= 1000)
{
num/=1000;
i++;
}
num = Math.round(num*1000)/1000;
if(num>=1000)
{
num/=1000;
i++;
num = Math.round(num*1000)/1000;
} //deals with rounding errors
num = num.toString();
if(num.indexOf('.') == -1) num += '.000'
else
{
dec = num.indexOf('.');
while(num.slice(dec,num.length).length < 4) num += '0' //adds trailing 0s (if needed) to stop the numbers jumping around.
}
return num +" "+ nums[i - 1]
}