W3 手风琴 - 默认打开/页面加载

Question

我正在遵循W3手风琴指南.我想知道如何修改代码，以便它们在默认情况下或在页面加载时打开。

以下是其功能操作方法示例的链接：

https://www.w3schools.com/howto/tryit.asp?filename=tryhow_js_accordion_symbol

谢谢

Answer 1

将脚本编辑为：

这将启动面板最初具有最大高度，直到之后等待。

var acc = document.getElementsByClassName("accordion");
var i;
for (i = 0; i < acc.length; i++) {
  var panel = acc[i].nextElementSibling;
  panel.style.maxHeight = panel.scrollHeight + "px";
  acc[i].onclick = function() {
    this.classList.toggle("active");
    var panel = this.nextElementSibling;
    if (panel.style.maxHeight) {
      panel.style.maxHeight = null;
    } else {
      panel.style.maxHeight = panel.scrollHeight + "px";
    }
  }
}

button.accordion {
  background-color: #eee;
  color: #444;
  cursor: pointer;
  padding: 18px;
  width: 100%;
  border: none;
  text-align: left;
  outline: none;
  font-size: 15px;
  transition: 0.4s;
}
button.accordion.active,
button.accordion:hover {
  background-color: #ddd;
}
button.accordion:after {
  content: '02B';
  color: #777;
  font-weight: bold;
  float: right;
  margin-left: 5px;
}
button.accordion.active:after {
  content: "2212";
}
div.panel {
  padding: 0 18px;
  background-color: white;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.2s ease-out;
}

<h2>Accordion with symbols</h2>
<p>In this example we have added a "plus" sign to each button. When the user clicks on the button, the "plus" sign is replaced with a "minus" sign.</p>
<button class="accordion">Section 1</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>
<button class="accordion">Section 2</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>
<button class="accordion">Section 3</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>

如果你不喜欢它，你可以在加载时使用jQuery点击所有这些。

var acc = document.getElementsByClassName("accordion");
var i;
for (i = 0; i < acc.length; i++) {
  acc[i].onclick = function() {
    var panel = this.nextElementSibling;
    this.classList.toggle("active");
    var panel = this.nextElementSibling;
    if (panel.style.maxHeight) {
      panel.style.maxHeight = null;
    } else {
      panel.style.maxHeight = panel.scrollHeight + "px";
    }
  }
  acc[i].click();
}

button.accordion {
  background-color: #eee;
  color: #444;
  cursor: pointer;
  padding: 18px;
  width: 100%;
  border: none;
  text-align: left;
  outline: none;
  font-size: 15px;
  transition: 0.4s;
}
button.accordion.active,
button.accordion:hover {
  background-color: #ddd;
}
button.accordion:after {
  content: '02B';
  color: #777;
  font-weight: bold;
  float: right;
  margin-left: 5px;
}
button.accordion.active:after {
  content: "2212";
}
div.panel {
  padding: 0 18px;
  background-color: white;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.2s ease-out;
}

<h2>Accordion with symbols</h2>
<p>In this example we have added a "plus" sign to each button. When the user clicks on the button, the "plus" sign is replaced with a "minus" sign.</p>
<button class="accordion">Section 1</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>
<button class="accordion">Section 2</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>
<button class="accordion">Section 3</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>

倒数第二行代码只是单击所有这些代码。(@Michael 科克 感谢您的提醒！以为这是一个jQuery函数。

Answer 2

在要打开的索引上触发.click()。 acc[0].click()将打开第一个。

var acc = document.getElementsByClassName("accordion");
var i;
for (i = 0; i < acc.length; i++) {
  acc[i].onclick = function() {
    this.classList.toggle("active");
    var panel = this.nextElementSibling;
    if (panel.style.maxHeight) {
      panel.style.maxHeight = null;
    } else {
      panel.style.maxHeight = panel.scrollHeight + "px";
    }
  };
}
acc[0].click();

button.accordion {
    background-color: #eee;
    color: #444;
    cursor: pointer;
    padding: 18px;
    width: 100%;
    border: none;
    text-align: left;
    outline: none;
    font-size: 15px;
    transition: 0.4s;
}
button.accordion.active, button.accordion:hover {
    background-color: #ddd;
}
button.accordion:after {
    content: '02B';
    color: #777;
    font-weight: bold;
    float: right;
    margin-left: 5px;
}
button.accordion.active:after {
    content: "2212";
}
div.panel {
    padding: 0 18px;
    background-color: white;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.2s ease-out;
}

<h2>Accordion with symbols</h2>
<p>In this example we have added a "plus" sign to each button. When the user clicks on the button, the "plus" sign is replaced with a "minus" sign.</p>
<button class="accordion">Section 1</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>
<button class="accordion">Section 2</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>
<button class="accordion">Section 3</button>
<div class="panel">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>