This js allows copying a clicked word in an html element to var "str". But I want to grab a word in an iframe src. I modified the js to target the iframe id #USCF_CUST and grab the clicked word, but it doesn't seem to work. The clicked word is not selected and copied to var "str". Can anyone tell me why?

<div class = "clickable">The rain in Spain falls mainly in the plane.</div>

 $(".clickable").click(function(e) {
 s = window.getSelection(); var range = s.getRangeAt(0); var node = s.anchorNode;
 while (range.toString().indexOf(' ') != 0) {range.setStart(node, (range.startOffset - 1));}
 range.setStart(node, range.startOffset + 1);
 do {range.setEnd(node, range.endOffset + 1);}
 while (range.toString().indexOf(' ') == -1 && range.toString().trim() != '');
 str = range.toString().trim(); alert (str);
});

But the above js doesn't work (it does nothing) in this instance:

<iframe id = 'USCF_CUST' src= url_2 ></iframe>

 $("#USCF_CUST").click(function(e) {
 s = window.getSelection(); var range = s.getRangeAt(0); var node = s.anchorNode;
 while (range.toString().indexOf(' ') != 0) {range.setStart(node, (range.startOffset - 1));}
 range.setStart(node, range.startOffset + 1);
 do {range.setEnd(node, range.endOffset + 1);}
 while (range.toString().indexOf(' ') == -1 && range.toString().trim() != '');
 str = range.toString().trim(); alert (str);
});