js 獲取選中文字

/*獲取選中的文字*/
var _getSelectedText = function() {
 if (window.getSelection) {
  return window.getSelection().toString();
 } else if (document.getSelection) {
  return document.getSelection();
 } else if (document.selection) {
  return document.selection.createRange().text;
 }else{
  return "";
 }
}