Javascript 仅在打开时在引导accordion中加载iFrame

我试图让iframes在bootstrap 3手风琴内，仅在物品打开时加载。现在，当页面加载时，所有iFrame都同时加载，这会导致页面长时间加载。如何在打开手风琴项目之前停止加载iFrame

这是我的折叠代码：

<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
<div class="panel panel-default">
    <div class="panel-heading" role="tab" id="heading1">
        <h4 class="panel-title">
            <a class="collapsed" data-toggle="collapse" data-parent="#accordion" href="#collapse1" aria-expanded="false" aria-controls="collapse1">
                Title 1 goes here
            </a>
        </h4>
    </div>
    <div id="collapse1" class="panel-collapse collapse" role="tabpanel" aria-labelledby="heading1">
        <ul class="list-group">
            <li class="list-group-item"> <iframe src="http://www.google.com"></iframe> </li>
        </ul>
    </div>
</div>
<div class="panel panel-default">
    <div class="panel-heading" role="tab" id="heading2">
        <h4 class="panel-title">
            <a class="collapsed" data-toggle="collapse" data-parent="#accordion" href="#collapse2" aria-expanded="false" aria-controls="collapse2">
                Title 2 goes here
            </a>
        </h4>
    </div>
    <div id="collapse2" class="panel-collapse collapse" role="tabpanel" aria-labelledby="heading2">
        <ul class="list-group">
            <li class="list-group-item"> <iframe src="http://www.yahoo.com"></iframe> </li>
        </ul>
    </div>
</div>

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您可以将SRC属性保留为空，然后在打开手风琴项目时挂接/设置自己的事件侦听器，以设置iframe的SRC属性