JavaScript converts numeric values to amount format (separating thousand points and automatically increasing the decimal point) _javascript tips

In the project encountered need to convert a number similar to the ' 450000 ' to accounting for the format used, ' 450,000.00 ', separating the Thousand and the decimal point after the two digits are not enough to automatically fill, has been recorded in several ways to achieve

PS: If you do not consider the following decimal point, the quickest way:

"12345678". Replace (/[0-9]+? =(?:( [0-9] {3})) +$)/g,function (a) {return + ', '}); Output 12 345 678

1. Implemented in a circular manner

function Formatnum (str) {
 var newstr = "";
 var count = 0;

 if (Str.indexof (".")  ==-1) {for
  (var i=str.length-1;i>=0;i--) {
   if (count% 3 = 0 && count!= 0) {
    newstr = Str.charat (i) + "," + Newstr;
   } else{
    newstr = Str.charat (i) + newstr;
   }
   count++;
  }
  str = newstr + ". 00"; Two-bit
  console.log (str)
 }
 else
 {for
  (var i = Str.indexof (".") after the decimal point is automatically filled -1;i>=0;i--) {
   if (count% 3 = 0 && count!= 0) {
    newstr = Str.charat (i) + "," + newstr;//hit a multiple of 3 plus "," Number
   }else{
    newstr = Str.charat (i) + newstr;//character story pick up
   }
   count++;
  str = newstr + (str + "+"). substr ((str + ")" IndexOf ("."), 3);
  Console.log (str)
 }
}

formatnum (' 13213.24 ');//Output 13,213.34
formatnum (' 132134.2 ');//Output 132, 134.20
formatnum (' 132134 ');//Output 132,134.00
formatnum (' 132134.236 ');//Output 132,134.236

2. Use regular (relatively insufficient is still have to judge the number of digits after the decimal point, there are more intelligent regular please notify me ~)

function Regexnum (str) {
 var regex =/(\d) (? = (\d\d\d) + (?!) \d))/g;

 if (Str.indexof (".") = = 1) {

  str= str.replace (Regex, ', ') + '.
  Console.log (str)

 }else{
  var newstr = Str.split ('. ');
  var str_2 = newstr[0].replace (Regex, ', ');

  if (newstr[1].length <= 1) { 
   //Only one time after the decimal point
   str_2 = str_2 + '. ' + newstr[1] + ' 0 ';
   Console.log (str_2)

  }else if (Newstr[1].length > 1) { 
   //decimal point after two digits
   var decimals = newstr[1].substr (0,2 );
   var srt_3 = str_2 + '. ' + decimals;
   Console.log (Srt_3)}}
;
Regexnum (' 23424224 '); Output 2,42,224.00 
regexnum (' 23424224.2 ');//Output 2,42,224.20
regexnum (' 23424224.22 ');//Output 2,42,224.22
Regexnum (' 23424224.233 '); Output 2,42,224.23 

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