Javascript selection的兼容性写法介绍

function getSelectedText() { //this function code is borrowed from: http://www.codetoad.com/javascript_get_selected_text.asp

var txt = "";
if (window.getSelection) {
txt = window.getSelection();
} else if (window.document.getSelection) {
txt = window.document.getSelection();
} else if (window.document.selection) {
txt = window.document.selection.createRange().text;
}
return txt;
}