Javascript String byteLength()

String.prototype.byteLength = function(){

 var count = 0;//from www .ja  va2  s .  com
 for(var i=0;i<this.length;i++)
  if(this.charCodeAt(i) >= 00000000 && this.charCodeAt(i) <= 0x0000007F)
   count++
  else if(this.charCodeAt(i) >= 0x00000080 && this.charCodeAt(i) <= 0x000007FF)
   count += 2
  else if(this.charCodeAt(i) >= 0x00000800 && this.charCodeAt(i) <= 0x0000FFFF)
   count += 3
  else if(this.charCodeAt(i) >= 0x00010000 && this.charCodeAt(i) <= 0x001FFFFF)
   count += 4
 return count
}

String.prototype.byteLength = function() {
 /**/*from  w w  w.  j ava 2  s  .co m*/
  * JavaScript only includes the natural logarithm method, but it does have some useful constants 
  *  for certain values, so here is how we calculate log256 x:
  * log256 x = log2 x / log2 256 <=> log256 x = log2 x / 8 (8 will now be known as LOG2_256)
  * log2 x = logE x / logE 2 (JavaScript has a constant value for logE 2 => Math.LN2)
  *  
  * log256 x = (logE x / Math.LN2) / LOG2_256 <=> log256 x = logE x / (LOG2_256 * Math.LN2)
  *
  * The final part of the calculation requires us to round up regardless of how small the
  *  decimal portion, this means that if the value is not exactly whole, it has one more byte of information.
  */
 var total = 0;
 var LOG2_256 = 8;
 var LN2x8 = Math.LN2 * LOG2_256;

 for(var i = 0; i < this.length; i++)
  total += Math.ceil(Math.log(this[i].charCodeAt()) / LN2x8);

 return total;
};