resources/src/jquery/jquery.byteLength.js

   1 /**
   2  * @class jQuery.plugin.byteLength
   3  * @author Jan Paul Posma, 2011
   4  * @author Timo Tijhof, 2012
   5  * @author David Chan, 2013
   6  */
   7
   8 /**
   9  * Calculate the byte length of a string (accounting for UTF-8).
  10  *
  11  * @static
  12  * @inheritable
  13  * @param {string} str
  14  * @return {number}
  15  */
  16 jQuery.byteLength = function ( str ) {
  17         // This basically figures out how many bytes a UTF-16 string (which is what js sees)
  18         // will take in UTF-8 by replacing a 2 byte character with 2 *'s, etc, and counting that.
  19         // Note, surrogate (\uD800-\uDFFF) characters are counted as 2 bytes, since there's two of them
  20         // and the actual character takes 4 bytes in UTF-8 (2*2=4). Might not work perfectly in
  21         // edge cases such as illegal sequences, but that should never happen.
  22
  23         // https://en.wikipedia.org/wiki/UTF-8#Description
  24         // The mapping from UTF-16 code units to UTF-8 bytes is as follows:
  25         // > Range 0000-007F: codepoints that become 1 byte of UTF-8
  26         // > Range 0080-07FF: codepoints that become 2 bytes of UTF-8
  27         // > Range 0800-D7FF: codepoints that become 3 bytes of UTF-8
  28         // > Range D800-DFFF: Surrogates (each pair becomes 4 bytes of UTF-8)
  29         // > Range E000-FFFF: codepoints that become 3 bytes of UTF-8 (continued)
  30
  31         return str
  32                 .replace( /[\u0080-\u07FF\uD800-\uDFFF]/g, '**' )
  33                 .replace( /[\u0800-\uD7FF\uE000-\uFFFF]/g, '***' )
  34                 .length;
  35 };
  36
  37 /**
  38  * @class jQuery
  39  * @mixins jQuery.plugin.byteLength
  40  */