JS 父窗口向子窗口传值问题（window.open()）

方法一~~~~~~~~~~~~~~~~~~~~~~主窗口：<input name="" type="button"  onclick="newpage()"/><script>var a = "12345";function newpage(){window.open("子窗口.html" + "?" + a);}</script>子窗口.html<script>var addstr= document.URL;var num=addstr.indexOf("?") addstr=addstr.substr(num+1);alert(addstr);</script> 方法二：~~~~~~~~~~~~~~~~~~~~~~~主窗口：<input id="hid" type="hidden" value="" /><input name="" type="button"  onclick="newpage()"/><script>var a = "12345";function newpage(){document.getElementById("hid").value = a;window.open("2.html");}</script>子窗口：<script>var prtW = window.opener;var prtA;if(prtW!=null){prtA = prtW.document.getElementById("hid").value;alert(prtA);}</script>