Get Text Selection

function selectedText() {
  if (document.getSelection) {
    var str = document.getSelection();
    if (window.RegExp) {
      var regstr = unescape("%20%20%20%20%20");
      var regexp = new RegExp(regstr, "g");
      str = str.replace(regexp, "");
    }
  } else if (document.selection && document.selection.createRange) {
    var range = document.selection.createRange();
    var str = range.text;
  } else {
    var str = "";
  }
  return str;
}

Working example: Try select some text anywhere in this page and press