how to get selected text from iframe with javascript?

document.getSelection

Is on the outer document. To get the selection of the document in the iframe you need to grab the inner document:

var iframe= document.getElementById('my');var idoc= iframe.contentDocument || iframe.contentWindow.document; // ie compatibilityidoc.getSelection()

Note however that WebKit does not support document.getSelection() or document.selection. Try replacing it with window.getSelection() which works in both Firefox and WebKit, but returns a selection object (a collection/wrapper around Ranges), which needs stringing:

var idoc= iframe.contentDocument || iframe.contentWindow.document;var iwin= iframe.contentWindow || iframe.contentDocument.defaultView;''+iwin.getSelection()

I'm not sure what the point of this is:

if (window.RegExp) {  var regstr = unescape("%20%20%20%20%20");  var regexp = new RegExp(regstr, "g");  str = str.replace(regexp, "");}

RegExp is basic JavaScript dating back to the very earliest version; it will always be there, you don't have to sniff for it. The URL-encoding of multiple spaces is quite unnecessary. You don't even need RegExp as such, a string replace could be written as:

str= str.split('     ').join('');

You need to get the selection from the document/window in the iframe.

function getIframeSelectionText(iframe) {  var win = iframe.contentWindow;  var doc = win.document;  if (win.getSelection) {    return win.getSelection().toString();  } else if (doc.selection && doc.selection.createRange) {    return doc.selection.createRange().text;  }}var iframe = document.getElementById("my");alert(getIframeSelectionText(iframe));

You can't access data inside an iframe that is from a domain different than yours.This is due to the Same origin policy.