How to pass value from Child window to Parent Window

<mce:script type="text/javascript"><!-- function submitWeight() { var weight = document.getElementsByName('weight')[0].value; var weight_p = document.getElementsByName('weight_p')[0].value; window.opener.document.getElementsByName('weight')[0].value = weight; window.opener.document.getElementsByName('weight_p')[0].value = weight_p; this.close(); } // --></mce:script>