How to pick element inside iframe using document.getElementById
问题 I have a iframe like this <iframe name=\"myframe1\" id=\"myframe1\" width=\"100%\" height=\"100%\" src=\"a.html\"> <html> <head></head> <frameset name=\"myframe2\" cols=\"0%, 100%\" border=\"0\" frameBorder=\"0\" frameSpacing=\"0\"> <frame name=\"page1\" src=\"c.html\" scrolling=\"no\"></frame> <frame name=\"page2\" src=\"d.html\" > <html> <head></head> <body id=\"top\"> <div id=\"div1\"> <div id=\"div2\"> <div id=\"div3\"> <ul id=\"x\"> <li>a</li> <li>b</li> </ul> </div> </div> </div> </body