Floating away...

abc123 · 11-21-2002, 02:20 AM

has anybody had experience with float calculation ( or just plain decimals ) with javascript...

here is an example:

Code:

<html>
<body>
<input type="text" name="abx" value="800" />
<input type="text" name="abz" value="1.12" />


<script language="javascript">

	function testIt(){
		var f1 = parseFloat(abx.value);
		var f2 = parseFloat(abz.value);
		var re = f1*f2;
		alert("result: " + re);
	}

</script>
<input type="button" onclick="testIt();" value="Click Me" />
</body>
</html>

you would, of course, expect to see "896.0" as the answer..

however if you try it you will get "896.00000000000001" ...

anyone know whats up with this and / or a mathematical work-around?

sde · 11-21-2002, 11:45 AM

i found a handy script for formatting numbers .. kinda long, but it works.

Code:

 <html>
<body>
<input type="text" name="abx" value="800" />
<input type="text" name="abz" value="1.12" />


  <SCRIPT language="JavaScript">
 <!-- Hide from older browsers
   // Original JavaScript code by Duncan Crombie: dcrombie@chirp.com.au
   // Please acknowledge use of this code by including this header.

   // CONSTANTS
  var separator = ",";  // use comma as 000's separator
  var decpoint = ".";  // use period as decimal point
  var percent = "%";
  var currency = "$";  // use dollar sign for currency

  function formatNumber(number, format, print) {  // use: formatNumber(number, "format")
    if (print) document.write("formatNumber(" + number + ", \"" + format + "\")<br>");

    if (number - 0 != number) return null;  // if number is NaN return null
    var useSeparator = format.indexOf(separator) != -1;  // use separators in number
    var usePercent = format.indexOf(percent) != -1;  // convert output to percentage
    var useCurrency = format.indexOf(currency) != -1;  // use currency format
    var isNegative = (number < 0);
    number = Math.abs (number);
    if (usePercent) number *= 100;
    format = strip(format, separator + percent + currency);  // remove key characters
    number = "" + number;  // convert number input to string

     // split input value into LHS and RHS using decpoint as divider
    var dec = number.indexOf(decpoint) != -1;
    var nleftEnd = (dec) ? number.substring(0, number.indexOf(".")) : number;
    var nrightEnd = (dec) ? number.substring(number.indexOf(".") + 1) : "";

     // split format string into LHS and RHS using decpoint as divider
    dec = format.indexOf(decpoint) != -1;
    var sleftEnd = (dec) ? format.substring(0, format.indexOf(".")) : format;
    var srightEnd = (dec) ? format.substring(format.indexOf(".") + 1) : "";

     // adjust decimal places by cropping or adding zeros to LHS of number
    if (srightEnd.length < nrightEnd.length) {
      var nextChar = nrightEnd.charAt(srightEnd.length) - 0;
      nrightEnd = nrightEnd.substring(0, srightEnd.length);
      if (nextChar >= 5) nrightEnd = "" + ((nrightEnd - 0) + 1);  // round up

 // patch provided by Patti Marcoux 1999/08/06
      while (srightEnd.length > nrightEnd.length) {
        nrightEnd = "0" + nrightEnd;
      }

      if (srightEnd.length < nrightEnd.length) {
        nrightEnd = nrightEnd.substring(1);
        nleftEnd = (nleftEnd - 0) + 1;
      }
    } else {
      for (var i=nrightEnd.length; srightEnd.length > nrightEnd.length; i++) {
        if (srightEnd.charAt(i) == "0") nrightEnd += "0";  // append zero to RHS of number
        else break;
      }
    }

     // adjust leading zeros
    sleftEnd = strip(sleftEnd, "#");  // remove hashes from LHS of format
    while (sleftEnd.length > nleftEnd.length) {
      nleftEnd = "0" + nleftEnd;  // prepend zero to LHS of number
    }

    if (useSeparator) nleftEnd = separate(nleftEnd, separator);  // add separator
    var output = nleftEnd + ((nrightEnd != "") ? "." + nrightEnd : "");  // combine parts
    output = ((useCurrency) ? currency : "") + output + ((usePercent) ? percent : "");
    if (isNegative) {
      // patch suggested by Tom Denn 25/4/2001
      output = (useCurrency) ? "(" + output + ")" : "-" + output;
    }
    return output;
  }

  function strip(input, chars) {  // strip all characters in 'chars' from input
    var output = "";  // initialise output string
    for (var i=0; i < input.length; i++)
      if (chars.indexOf(input.charAt(i)) == -1)
        output += input.charAt(i);
    return output;
  }

  function separate(input, separator) {  // format input using 'separator' to mark 000's
    input = "" + input;
    var output = "";  // initialise output string
    for (var i=0; i < input.length; i++) {
      if (i != 0 && (input.length - i) % 3 == 0) output += separator;
      output += input.charAt(i);
    }
    return output;
  }



	function testIt(){
		var f1 = parseFloat(abx.value);
		var f2 = parseFloat(abz.value);
		var re = f1*f2;
		var n = formatNumber(re, "##0.#")
		
		alert("result: " + n);
	}	
// Stop hiding -->

</script>
<input type="button" onclick="testIt();" value="Click Me" />
</body>
</html>

here is a page with examples of formats: http://members.ozemail.com.au/~dcrombie/format.html

11-21-2002, 03:05 PM

Er, Didnt really say what was the problem that needed to be solved... to just get 896 do parseInt(re)

Or just do

Code:

document.write("result : " + (parseInt(re*1000))/1000);

That should work to keep 3 the number to decimal places...

Lets say we had 123.4567 It would multiply by a thousand and we would get 123456.7, parseInt it. we have 123456, divide 123.456 . Done

abc123 · 11-21-2002, 03:41 PM

actually i wanted it to a "fixed" two decimal value of 100000 of a cent accuracy, this is how i did it:

Code:

	function t2(v){
		tmpv = v;
		suffix = ""
		do0 = false;
		if(Math.round(v) == v){
			suffix = ".00";
			res = v+suffix;
			return res;
		}else{
			v = v+"";
			tmpy = v.indexOf(".");

			if(tmpy+6 < v.length){
				tmpRem = v.substring(tmpy, tmpy+6);
				tmpz = Math.floor(v);
				return tmpz+".00";
			}

		}

		tmpv = tmpv * 100;
		tmpv = Math.round(tmpv);
		if(tmpv % 10 == 0 || tmpv % -10 == 0){
			do0 = true;
		}
		tmpv = tmpv / 100;
		if(do0){
			tmpv = tmpv + "0";
		}
		return tmpv;
	}

unfortunately, or fortunately, after writing that i discovered this function:

Code:

var x = 16.000000000000001;
alert(x.toFixed(2));

hmm, oh well

at least that was only a small section of what i had to do, the code wasn't a waste.