ts to extract.<DT><B>Returns:</B><DD>The specified substring. If the sum of <code>offset</code> and 
   <code>count</code> exceeds the <code>length</code>, then all 16-bit 
   units to the end of the data are returned.<DT><B>Throws:</B><DD><CODE><A HREF="../../../org/w3c/dom/DOMException.html">DOMException</A></CODE> - INDEX_SIZE_ERR: Raised if the specified <code>offset</code> is 
   negative or greater than the number of 16-bit units in 
   <code>data</code>, or if the specified <code>count</code> is 
   