https://www.ls-comp.ru/js/number_format.js

1		function number_format(number, decimals, dec_point, thousands_sep){  
2		  var exponent = "";  
3		  var numberstr = number.toString ();  
4		  var eindex = numberstr.indexOf ("e");  
5		 var i, z;  
6		  if(eindex > -1){  
7		    exponent = numberstr.substring (eindex);  
8		    number = parseFloat (numberstr.substring (0, eindex));  
9		  }  
10		    
11		  if(decimals != null){  
12		    var temp = Math.pow (10, decimals);  
13		    number = Math.round (number * temp) / temp;  
14		  }  
15		  var sign = number < 0 ? "-" : "";  
16		  var integer = (number > 0 ?   
17		      Math.floor (number) : Math.abs (Math.ceil (number))).toString ();  
18		    
19		  var fractional = number.toString ().substring (integer.length + sign.length);  
20		  dec_point = dec_point != null ? dec_point : ".";  
21		  fractional = decimals != null && decimals > 0 || fractional.length > 1 ? (dec_point + fractional.substring (1)) : "";  
22		  if(decimals != null && decimals > 0){  
23		    for(i = fractional.length - 1, z = decimals; i < z; ++i)  
24		      fractional += "0";  
25		  }  
26		    
27		  thousands_sep = (thousands_sep != dec_point || fractional.length == 0) ?   
28		                  thousands_sep : null;  
29		  if(thousands_sep != null && thousands_sep != ""){  
30		  for (i = integer.length - 3; i > 0; i -= 3)  
31		   integer = integer.substring (0 , i) + thousands_sep + integer.substring (i);  
32		  }  
33		  return sign + integer + fractional + exponent;  
34		}