Selection.removeRange()

sel.removeRange(range)

/* Programmatically, more than one range can be selected.
 * This will remove all ranges except the first. */
s = window.getSelection();
if(s.rangeCount > 1) {
 for(var i = 1; i < s.rangeCount; i++) {
  s.removeRange(s.getRangeAt(i));
 }
}