code: function(editor, fn) {
  			var content = String(editor.getContent());
  			var il = content.length;
  			var exprStart = editor.getCaretPos() - 1;
  			var exprEnd = exprStart + 1;
  				
  			// start by searching left
  			while (exprStart >= 0 && fn(content.charAt(exprStart), exprStart, content)) exprStart--;
  			
  			// then search right
  			while (exprEnd < il && fn(content.charAt(exprEnd), exprEnd, content)) exprEnd++;
  			
  			if (exprEnd > exprStart) {
  				return range([++exprStart, exprEnd]);
  			}
  		}
docs: Find expression bounds in current editor at caret position.
  On each character a <code>fn</code> function will be called and must
  return <code>true</code> if current character meets requirements,
  <code>false</code> otherwise
  @param {IEmmetEditor} editor
  @param {Function} fn Function to test each character of expression
  @return {Range}