resources/jquery/jquery.byteLimit.js

   1 /**
   2  * jQuery byteLimit
   3  */
   4 ( function( $ ) {
   5
   6         /**
   7          * Enforces a byte limit to a textbox, so that UTF-8 entries are not arbitrarily truncated.
   8          */
   9         $.fn.byteLimit = function( limit ) {
  10                 return $(this).attr( 'maxLength', limit ).keypress( function( e ) {
  11                         // first check to see if this is actually a character key
  12                         // being pressed.
  13                         // Based on key-event info from http://unixpapa.com/js/key.html
  14                         // jQuery should also normalize e.which to be consistent cross-browser,
  15                         // however the same check is still needed regardless of jQuery.
  16
  17                         // Note: At the moment, for some older opera versions (~< 10.5)
  18                         // some special keys won't be recognized (aka left arrow key).
  19                         // Backspace will be, so not big issue.
  20
  21                         if ( e.which === 0 || e.charCode === 0 || e.which === 8 ||
  22                                 e.ctrlKey || e.altKey || e.metaKey )
  23                         {
  24                                 return true; //a special key (backspace, etc) so don't interfere.
  25                         }
  26
  27                         // This basically figures out how many bytes a UTF-16 string (which is what js sees)
  28                         // will take in UTF-8 by replacing a 2 byte character with 2 *'s, etc, and counting that.
  29                         // Note, surrogate (\uD800-\uDFFF) characters are counted as 2 bytes, since there's two of them
  30                         // and the actual character takes 4 bytes in UTF-8 (2*2=4). Might not work perfectly in edge cases
  31                         // such as illegal sequences, but that should never happen.
  32
  33                         var len = this.value.replace( /[\u0080-\u07FF\uD800-\uDFFF]/g, '**' ).replace( /[\u0800-\uD7FF\uE000-\uFFFF]/g, '***' ).length;
  34                         // limit-3 as this doesn't count character about to be inserted.
  35                         if ( len > ( limit-3 ) ) {
  36                                 e.preventDefault();
  37                         }
  38                 });
  39         };
  40
  41 } )( jQuery );