Javascript window object

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In Javascript, let\'s say we have a main page (main.html) which contains an </code> (<code>iframe.html</code>)</p> <p>Now inside this <code>ifr <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script> <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-5408099190056760" data-ad-slot="7305827575" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> <div class="relativetags"> 相关标签: </div> </div> <div class="fly-panel detail-box" id="flyReply"> <fieldset class="layui-elem-field layui-field-title" style="text-align: center;"> <legend>2条回答</legend> </fieldset> <ul class="jieda" id="jieda"> <li data-id="111"> <a name="item-1111111111"></a> <div class="detail-about detail-about-reply"> <a class="fly-avatar" href="https://www.e-learn.cn/qa/u-119.html"> <img src="https://www.e-learn.cn/qa/data/avatar/000/00/01/small_000000119.jpg" alt=" "> </a> <div class="fly-detail-user"> <a href="https://www.e-learn.cn/qa/u-119.html" class="fly-link"> <cite>無奈伤痛 </cite> </a> </div> <div class="detail-hits"> <span>2021-02-13 18:50</span> </div> </div> <div class="detail-body jieda-body photos"> <p><code>iframe</code>s (and <code>frame</code>s) are their own windows, even though in the case of <code>iframe</code>s they look like they're part of the main document's window. So yes, to refer to the main document's window, they'd use <code>parent</code> (or <code>window.parent</code> if you want to be verbose, but clear), because they are separate objects. This is partially necessary because a lot of the things in <code>document</code> end up as properties on the containing <code>window</code>.</p> <p>If you think about it, it makes sense: The purpose of an <code>iframe</code> is to embed independently-sourced content within the page. If the main page and the <code>iframe</code>(s) on it shared a single <code>window</code> object, they'd be sharing global context, and quite possibly conflicting with one another.</p> <p>Gratuitous live example:</p> <p>Parent's HTML:</p> <pre><code><p>I'm the parent window</p> <iframe width="500" height="500" src="http://jsbin.com/iyogir"></iframe> </code></pre> <p>Parent's JavaScript:</p> <pre><code>function foo() { display("<code>foo</code> called!"); } function display(msg) { var p = document.createElement('p'); p.innerHTML = msg; document.body.appendChild(p); } </code></pre> <p>Child's HTML:</p> <pre><code><p>I'm in the frame</p> <input type='button' id='theButton' value='Click Me'> </code></pre> <p>Child's JavaScript:</p> <pre><code>window.onload = function() { document.getElementById('theButton').onclick = function() { var p = window.parent; if (!p) { display("Can't find parent window"); } else if (typeof p.foo !== "function") { display("Found parent window, but can't find <code>foo</code> function on it"); } else { display("Calling parent window's <code>foo</code> function."); p.foo(); } }; function display(msg) { var p = document.createElement('p'); p.innerHTML = msg; document.body.appendChild(p); } }; </code></pre> <div class="appendcontent"> </div> </div> <div class="jieda-reply"> <span class="jieda-zan button_agree" type="zan" data-id='2192025'> <i class="iconfont icon-zan"></i> <em>0</em> </span> <span type="reply" class="showpinglun" data-id="2192025"> <i class="iconfont icon-svgmoban53"></i> 讨论(0) </span> <div class="jieda-admin"> </div> </div> <div class="comments-mod " style="display: none; float:none;padding-top:10px;" id="comment_2192025"> <div class="areabox clearfix"> <form class="layui-form" action=""> <div class="layui-form-item"> <label class="layui-form-label" style="padding-left:0px;width:60px;">发布评论:</label> <div class="layui-input-block" style="margin-left:90px;"> <input type="text" placeholder="不少于5个字" AUTOCOMPLETE="off" class="comment-input layui-input" name="content" /> <input type='hidden' value='0' name='replyauthor' /> </div> <div class="mar-t10"><span class="fr layui-btn layui-btn-sm addhuidapinglun" data-id="2192025">提交评论 </span></div> </div> </form> </div> <hr> <ul class="my-comments-list nav"> <li class="loading"> <img src='https://www.e-learn.cn/qa/static/css/default/loading.gif' align='absmiddle' />  加载中... </li> </ul> </div> </li> <li data-id="111"> <a name="item-1111111111"></a> <div class="detail-about detail-about-reply"> <a class="fly-avatar" href="https://www.e-learn.cn/qa/u-96.html"> <img src="https://www.e-learn.cn/qa/data/avatar/000/00/00/small_000000096.jpg" alt=" "> </a> <div class="fly-detail-user"> <a href="https://www.e-learn.cn/qa/u-96.html" class="fly-link"> <cite>自闭症患者 </cite> </a> </div> <div class="detail-hits"> <span>2021-02-13 19:15</span> </div> </div> <div class="detail-body jieda-body photos"> <p>The concept of <code>window</code> is tied to the <code>document</code>: There's one <code>window</code> per <code>document</code>, and one <code>document</code> per <code>window</code>.</p> <p>That means <code><iframe></code> elements, which have their own <code>document</code>, also have their own <code>window</code>, just like a pop-up window or the main navigator window.</p> <p>So, you'll indeed have to use <code>window.parent</code> to access the container of an <code><iframe></code> element, just like you have to use <code>window.opener</code> to access the owner of a pop-up window.</p> <p><strong>EDIT:</strong> Both <code>window.parent</code> and <code>parent.window</code> are valid expressions that return the same object. That's because the <code>window</code> object is the <em>default context</em> in scripting (unqualified names are parsed as members of <code>window</code>), and <code>window</code> objects have a <code>window</code> property that refers to themselves.</p> <p>So, <code>parent.window</code> is evaluated as <code>window.parent.window</code>, which is the same object as <code>window.parent</code>.</p> <p>That said, I do prefer using <code>window.parent</code>, to avoid the (minimal) overhead associated with the extra property access.</p> <div class="appendcontent"> </div> </div> <div class="jieda-reply"> <span class="jieda-zan button_agree" type="zan" data-id='2192024'> <i class="iconfont icon-zan"></i> <em>0</em> </span> <span type="reply" class="showpinglun" data-id="2192024"> <i class="iconfont icon-svgmoban53"></i> 讨论(0) </span> <div class="jieda-admin"> </div> </div> <div class="comments-mod " style="display: none; float:none;padding-top:10px;" id="comment_2192024"> <div class="areabox clearfix"> <form class="layui-form" action=""> <div class="layui-form-item"> <label class="layui-form-label" style="padding-left:0px;width:60px;">发布评论:</label> <div class="layui-input-block" style="margin-left:90px;"> <input type="text" placeholder="不少于5个字" AUTOCOMPLETE="off" class="comment-input layui-input" name="content" /> <input type='hidden' value='0' name='replyauthor' /> </div> <div class="mar-t10"><span class="fr layui-btn layui-btn-sm addhuidapinglun" data-id="2192024">提交评论 </span></div> </div> </form> </div> <hr> <ul class="my-comments-list nav"> <li class="loading"> <img src='https://www.e-learn.cn/qa/static/css/default/loading.gif' align='absmiddle' />  加载中... </li> </ul> </div> </li> <style> .laypage-main a, .laypage-main span { display: inline-block; } </style> </ul> <div class="layui-form layui-form-pane"> <form id="huidaform" name="answerForm" method="post"> <div class="layui-form-item layui-form-text"> <a name="comment"></a> <div class="layui-input-block"> <script type="text/javascript" src="https://www.e-learn.cn/qa/static/js/neweditor/ueditor.config.js"></script> <script type="text/javascript" src="https://www.e-learn.cn/qa/static/js/neweditor/ueditor.all.js"></script> <script type="text/plain" id="editor" name="content" style="width:100%;height:200px;"></script> <script type="text/javascript"> var isueditor=1; var editor = UE.getEditor('editor',{ //这里可以选择自己需要的工具按钮名称,此处仅选择如下五个 toolbars:[['source','fullscreen', '|', 'undo', 'redo', '|', 'bold', 'italic', 'underline', 'fontborder', 'strikethrough', 'removeformat', 'formatmatch', 'autotypeset', 'blockquote', 'pasteplain', '|', 'forecolor', 'backcolor', 'insertorderedlist', 'insertunorderedlist', 'selectall', 'cleardoc', '|', 'rowspacingtop', 'rowspacingbottom', 'lineheight', '|', 'customstyle', 'paragraph', 'fontfamily', 'fontsize', '|', 'indent', '|', 'justifyleft', 'justifycenter', 'justifyright', 'justifyjustify', '|', 'link', 'unlink', 'anchor', '|', 'simpleupload', 'insertimage', 'scrawl', 'insertvideo', 'attachment', 'map', 'insertcode', '|', 'horizontal', '|', 'preview', 'searchreplace', 'drafts']], initialContent:'', //关闭字数统计 wordCount:false, zIndex:2, //关闭elementPath elementPathEnabled:false, //默认的编辑区域高度 initialFrameHeight:250 //更多其他参数，请参考ueditor.config.js中的配置项 //更多其他参数，请参考ueditor.config.js中的配置项 }); editor.ready(function() { editor.setDisabled(); }); $("#editor").find("*").css("max-width","362px"); </script> </div> </div> <div class="layui-form-item"> <label for="L_vercode" class="layui-form-label">验证码</label> <div class="layui-input-inline"> <input type="text" id="code" name="code" value="" required lay-verify="required" placeholder="图片验证码" autocomplete="off" class="layui-input"> </div> <div class="layui-form-mid"> <span style="color: #c00;"><img class="hand" src="https://www.e-learn.cn/qa/user/code.html" onclick="javascript:updatecode();" id="verifycode"><a class="changecode" href="javascript:updatecode();"> 看不清?</a></span> </div> </div> <div class="layui-form-item"> <input type="hidden" value="1114045" id="ans_qid" name="qid"> <input type="hidden" id="tokenkey" name="tokenkey" value=''/> <input type="hidden" value="Javascript window object" id="ans_title" name="title"> <div class="layui-btn layui-btn-disabled" id="ajaxsubmitasnwer" >提交回复</div> </div> </form> </div> </div> <input type="hidden" value="1114045" id="adopt_qid" name="qid" /> <input type="hidden" id="adopt_answer" value="0" name="aid" /> </div> <div class="layui-col-md4">  <dl class="fly-panel fly-list-one"> <dt class="fly-panel-title">热议问题</dt>