parseInt .5

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  • Jeff Thies
    #1

    parseInt .5

    I've noticed that doing:

    var x=any number between -1 and 1, like 0.5

    parsInt(x)

    yields NaN.

    I was expecting zero. Is there another way of doing this?

    Jeff


    Tags: None
    • Lasse Reichstein Nielsen
      #2
      Re: parseInt .5

      "Jeff Thies" <nospam@nospam. net> writes:
      [color=blue]
      > I've noticed that doing:
      >
      > var x=any number between -1 and 1, like 0.5
      >
      > parsInt(x)
      >
      > yields NaN.
      >
      > I was expecting zero.[/color]

      I am getting 0, both for "0.5" and 0.5 (the number). I'm using Opera 7,
      what browser are you using?

      Hmm, let me check ... yes. Netscape 4:
      parseInt(0.5)
      gives NaN. The reason is that Netscape 4's toString turns 0.5 into the
      string ".5", not "0.5" as the other browsers I checked.
      [color=blue]
      > Is there another way of doing this[/color]

      Don't use numbers as arguments to parseInt, it's meant for strings.

      What are you trying to do?
      If you want to turn a number into an integer, use Math.round, Math.floor
      or Math.ceil.

      /L
      --
      Lasse Reichstein Nielsen - lrn@hotpop.com
      DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
      'Faith without judgement merely degrades the spirit divine.'

        Comment

        • Jeff Thies
          #3
          Re: parseInt .5

          > > I've noticed that doing:[color=blue][color=green]
          > >
          > > var x=any number between -1 and 1, like 0.5
          > >
          > > parsInt(x)
          > >
          > > yields NaN.
          > >
          > > I was expecting zero.[/color]
          >
          > I am getting 0, both for "0.5" and 0.5 (the number). I'm using Opera 7,
          > what browser are you using?[/color]

          Oh, I see that now.
          [color=blue]
          > Hmm, let me check ... yes. Netscape 4:[/color]

          Yep. You are right! I often use NS4 to develope in. The most primitive
          possible case, so to speak. It also doesn't empty form fields on refresh,
          which can be a real time saver when hacking through forms.

          [color=blue]
          > parseInt(0.5)
          > gives NaN. The reason is that Netscape 4's toString turns 0.5 into the
          > string ".5", not "0.5" as the other browsers I checked.
          >[color=green]
          > > Is there another way of doing this[/color]
          >
          > Don't use numbers as arguments to parseInt, it's meant for strings.
          >
          > What are you trying to do?[/color]

          Convert fractional degrees to Degrees Minutes Seconds (like latitude).
          [color=blue]
          > If you want to turn a number into an integer, use Math.round, Math.floor
          > or Math.ceil.[/color]

          I need -0.5 to be 0. I may be relying too heavily on implied data type
          conversions

          Here's what I cobbled up:

          (To get minutes, you take the fractional part of degrees and multiply by 60.
          Same with seconds. I tried to keep this from line wrapping!)

          // parseInt but returns 0 from fractions instead of NaN
          function parseMyInt(n){ if((n > -1) && (n < 1)){return 0;}
          return parseInt(n);
          }

          // add leading 0 if needed
          function formatIt(n){ n=Math.abs(n);
          if(n <10){return n + '0'}
          return n;
          }

          // decimal degrees to D M S
          function
          imalToDMS(decim al){
          var D=parseMyInt(de cimal);

          var Mfraction=(deci mal - D) * 60;
          var M=parseMyInt(Mf raction);

          var Sfraction=Math. abs(Mfraction - M);

          M=formatIt(M);

          if((decimal < 0) && (D == 0)){D = '-0'} // fix for -0D

          var S=formatIt(Math .round(Sfractio n * 60));

          return{D:D,M:M, S:S};
          }

          Cheers,
          Jeff
          [color=blue]
          >
          > /L
          > --
          > Lasse Reichstein Nielsen - lrn@hotpop.com
          > DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleDOM.ht[/color]
          ml>[color=blue]
          > 'Faith without[/color]


            Comment

            • Lasse Reichstein Nielsen
              #4
              Re: parseInt .5

              "Jeff Thies" <nospam@nospam. net> writes:
              [color=blue][color=green]
              >> What are you trying to do?[/color]
              >
              > Convert fractional degrees to Degrees Minutes Seconds (like latitude).[/color]
              ....[color=blue]
              > I need -0.5 to be 0.[/color]

              function sign(n) {
              return n?n<0?-1:1:0;
              }
              function roundTowardsZer o(n) {
              return sign(n)*Math.fl oor(Math.abs(n) );
              }
              [color=blue]
              > I may be relying too heavily on implied data type conversions[/color]

              Probably :)
              [color=blue]
              > Here's what I cobbled up:
              >
              > (To get minutes, you take the fractional part of degrees and multiply by 60.
              > Same with seconds. I tried to keep this from line wrapping!)[/color]

              What is -10.5 degrees in DMS?
              -10 degrees and 30 minutes
              or
              -10 degrees and -30 minutes?
              You return it as
              {D:"-10",M:"30",S:"0 0"}

              I can do that too, but are you sure it is what you want? :)
              [color=blue]
              > // add leading 0 if needed
              > function formatIt(n){ n=Math.abs(n);[/color]

              Can it be negative? Should the sign be discarded if it is?


              Try this:
              ---
              function sign(n) {
              return n?n<0?-1:1:0;
              }
              function LZ(n) {
              return (n<10?"0":"")+n ;
              }

              function imalToDMS(decim al) {
              var ds = sign(decimal);
              var decimal = Math.abs(decima l);
              var D = Math.floor(deci mal);
              var Mfraction = (decimal - D) * 60;
              var M = Math.floor(Mfra ction);
              var Sfraction = (Mfraction - M) * 60;
              var S = Math.round(Sfra ction);
              return {D:(ds<0?"-":"")+D,M:LZ(M) ,S:LZ(S)};
              }
              ---

              /L
              --
              Lasse Reichstein Nielsen - lrn@hotpop.com
              DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
              'Faith without judgement merely degrades the spirit divine.'

                Comment

                • Richard Cornford
                  #5
                  Re: parseInt .5

                  "Lasse Reichstein Nielsen" <lrn@hotpop.com > wrote in message
                  news:7k0rv6pp.f sf@hotpop.com.. .
                  <snip>[color=blue][color=green]
                  >>Convert fractional degrees to Degrees Minutes Seconds
                  >>(like latitude).[/color]
                  >...[color=green]
                  >> I need -0.5 to be 0.[/color]
                  >
                  >function sign(n) {
                  > return n?n<0?-1:1:0;
                  >}
                  >function roundTowardsZer o(n) {
                  > return sign(n)*Math.fl oor(Math.abs(n) );
                  >}[/color]
                  <snip>

                  If, and only if, the desired result can be expressed as a 32 bit signed
                  integer (or maybe 31 bits for safety) it should also be possible to
                  round a float towards zero by using an operator that would force the use
                  of the internal ToInt32 function (such as any bitwise operator) in a way
                  that doesn't otherwise change the number. Such as:-

                  function roundTowardsZer o_Int32(n) {
                  return (n|0);
                  }

                  Richard.


                    Comment

                    • Dr John Stockton
                      #6
                      Re: parseInt .5

                      JRS: In article <SCZEb.6093$wL6 .327@newsread1. news.atl.earthl ink.net>,
                      seen in news:comp.lang. javascript, Jeff Thies <nospam@nospam. net> posted
                      at Sat, 20 Dec 2003 15:09:38 :-[color=blue]
                      >
                      >// add leading 0 if needed
                      >function formatIt(n){ n=Math.abs(n);
                      >if(n <10){return n + '0'}
                      >return n;
                      >}[/color]


                      I think you need to spend considerably more time reading and testing,
                      and less time writing.

                      That function returns 50 for inputs of +5 & -5; and 00 for 0.

                      function LZ(x) {return(x<0||x> 9?"":"0")+x} // for integers

                      is reliable, and has the possible advantage of always returning a
                      string.

                      There is no leading zero function in the FAQ <FAQENTRY> bur perhaps
                      there should be; one so often sees repetitive coding for it.

                      <URL:http://www.merlyn.demo n.co.uk/js-maths.htm#LZ> refers.

                      --
                      © John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
                      <URL:http://jibbering.com/faq/> Jim Ley's FAQ for news:comp.lang. javascript
                      <URL:http://www.merlyn.demo n.co.uk/js-index.htm> jscr maths, dates, sources.
                      <URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links.

                        Comment

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