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HTML 

              
                
<h1>Toggling accordions using 5 different methods</h1>


<section>
  <details>
    <summary class=toggler_1>Pure HTML, zero JS, zero CSS [recommended 2022]</summary>
    <div class=tog_content>
      <p>The <code>summary</code> element acts as a button, and the element that follows is the hidden content.</p>
      <figure>
        <figcaption>HTML</figcaption>
        <pre><code class=language-markup spellcheck=false contenteditable>&lt;details&gt;
    &lt;summary&gt;Pure HTML accordian&lt;/summary&gt;
    &lt;div&gt;
        &lt;!-- Drop down content --&gt;
    &lt;/div&gt;
&lt;/details&gt;</code></pre>
      </figure>
    </div>
</section>


<section>
  <!-- Ref: https://www.w3.org/WAI/GL/wiki/Using_aria-expanded_to_indicate_the_state_of_a_collapsible_element -->

  <button class=toggler_1 aria-expanded=false onclick="this.setAttribute('aria-expanded',this.getAttribute('aria-expanded')==='false')">Toggle <strong>next sibling</strong> using <strong>inline</strong> JS [simplest]</button>

  
  <div class=toggled_1>
    <div class=tog_content>
      
      <h2 class=tog_title>Accessibily toggle a buttons <strong>next sibling</strong> using <strong>inline</strong> JS (on the button only).</h2>
      
      <figure>
        <figcaption>HTML <small>(with inline JavaScript)</small></figcaption>
        <pre><code class=language-markup spellcheck=false contenteditable>&lt;button class="toggler"
    onclick="this.setAttribute('aria-expanded', this.getAttribute('aria-expanded') === 'false');"
    aria-expanded="false"&gt;Toggle button&lt;/button&gt;
&lt;div class="toggled"&gt;Toggled content&lt;/div&gt;</code></pre>
      </figure>
      
      <figure>
        <figcaption>CSS</figcaption>
        <pre><code class=language-css spellcheck=false contenteditable>.toggler[aria-expanded="false"] + .toggled {
    overflow: hidden;
    visibility: hidden;
    opacity: 0;
    max-height: 0;
    transition:
        visibility 0s ease .6s,
        opacity .6s ease-in 0s,
        max-height .6s ease-out 0s;
}
.toggler[aria-expanded="true"] + .toggled {
    overflow: hidden;
    visibility: visible;
    opacity: 1;
    /* Ensure max-height is sufficient at min-width */
    max-height: 20rem;
    transition:
        visibility 0s ease 0s,
        opacity .6s ease-in 0s, 
        max-height .6s ease-out 0s;
}</code></pre>
      </figure>
      
    </div>
  </div>
</section>

 

 


<section>
  <label class=tog_container>

    <span class=toggler_2>Toggle <strong>next sibling</strong> with <strong>zero</strong> JavaScript</span>

    <input class=visually-hidden type=checkbox>

    <span class=toggled_2>
      <span class=tog_content>

        <em class=tog_title>Toggle <strong>next sibling</strong>. HTML &amp; CSS only, no JavaScript</em>

        <figure>
          <figcaption>HTML</figcaption>
            <pre><code class=language-markup spellcheck=false contenteditable>&lt;label&gt;
    &lt;span class="toggler"&gt;Toggle button&lt;/span&gt;
    &lt;input class="visually-hidden" type="checkbox"&gt;
    &lt;span class="toggled"&gt;Toggled content&lt;/span&gt;
&lt;/label&gt;</code></pre>
        </figure>

        <figure>
          <figcaption>CSS</figcaption>
            <pre><code class=language-css spellcheck=false contenteditable>.toggler, .toggled {display: block}
.toggled {
    overflow: hidden;
    visibility: hidden;
    opacity: 0;
    max-height: 0;
    transition: 
        visibility 0s ease .6s,
        opacity .6s ease-in 0s,
        max-height .6s ease-out 0s;
}
:checked + .toggled {
    visibility: visible;
    opacity: 1;
    /* Ensure max-height is sufficient at min-width */
    max-height: 50rem;
    transition-delay: 0s, 0s, 0s; /* unit "s" is required */
}</code></pre>
        </figure>
      
      </span>
    </span>

  </label>
</section>



<section>
  
  <div>
<button aria-expanded=false aria-controls=toggled_5
  onclick="(function(b){var s=b.getAttribute('aria-expanded')==='true',c=document.getElementById(b.getAttribute('aria-controls'));if(!c)return;c.setAttribute('style','max-height:'+c.scrollHeight+'px');b.setAttribute('aria-expanded',!s);c.setAttribute('aria-hidden',s);})(this);"
  class=toggler_3>
  Toggle a <strong>specified element</strong> using <strong>inline</strong> JS
</button>
  </div>

  <div class=toggled_5 id=toggled_5 aria-hidden=true>
    <div class=tog_content>

      <h2 class=tog_title>Accessibily toggle a buttons <strong>specified</strong> content panel using <strong>inline</strong> JS (on the button only). Button and content panel do not need to be siblings.</h2>

      <figure>
        <figcaption>HTML <small>(with inline JavaScript)</small></figcaption>
        <pre><code class=language-markup spellcheck=false contenteditable>&lt;button class="toggler"
    onclick="(function(b){var s=b.getAttribute('aria-expanded')==='true',c=document.getElementById(b.getAttribute('aria-controls'));if(!c)return;c.setAttribute('style','max-height:'+c.scrollHeight+'px');b.setAttribute('aria-expanded',!s);c.setAttribute('aria-hidden',s);})(this);"
    aria-controls="toggled"
    aria-expanded="false"&gt;Toggle button&lt;/button&gt;
&lt;div aria-hidden="true" id="toggled" class="toggled"&gt;Toggled content&lt;/div&gt;
</code></pre>
      </figure>
      
      <p>The <code>max-height</code> of the content panel is accurately calculated by the buttons inline JavaScript.</p>

      <figure>
        <figcaption>CSS</figcaption>
        <pre><code class=language-css spellcheck=false contenteditable>.toggled[aria-hidden] {
    overflow: hidden;
    visibility: hidden; /* Removes content from keyboard focus chain */
    opacity: 0;
    max-height: 0;
    transition: 
        visibility 0s linear .6s,
        opacity .6s ease-in,
        max-height .6s ease-out;
}
.toggled[aria-hidden="true"] {
    max-height: 0 !important; /* Overrides inline style */
}
.toggled[aria-hidden="false"] {
    visibility: visible;
    opacity: 1;
    max-height: 50em; /* Set more accurately inline by JavaScript */
    transition-delay: 0s, 0s, 0s;
    transition-timing-function: linear, linear, ease-out;
}
</code></pre>
      </figure>
      
      <p>See the full pen for details: <a target=_blank title="[new window]" href="https://codepen.io/2kool2/pen/aGOmxZ">Accordion expand/collapse using inline JavaScript</a></p>
      
      <p>Which also contains optional extensions to:</p>
      <ul>
        <li>Open from URL</li>
        <li>Open from anchor</li>
        <li>Scroll button to top</li>
        <li>Embed accordions</li>
        <li>Open a single accordion.</li>
      </ul>

    </div>
  </div>

</section>


 

<section>
  
  <div>
    <button class=toggler_3 data-toggler="#toggled_3">
      Toggle a <strong>specified element</strong> using JS
    </button>
  </div>

  <div class="toggled_3 xtoggled-long" id=toggled_3>
    <div class=tog_content>
      
      <h2 class=tog_title>Accessibily toggle a <strong>specified element</strong>, and account for variable height, using JavaScript</h2>
      
      <figure>
        <figcaption>HTML</figcaption>
        <pre><code class=language-markup spellcheck=false contenteditable>&lt;button data-toggler="#toggled"&gt;Toggle button&lt;/button&gt;
&lt;div id="toggled" class="toggled"&gt;Toggled content&lt;/div&gt;
</code></pre>
      </figure>

        <figure>
          <figcaption>CSS</figcaption>
            <pre><code class=language-css spellcheck=false contenteditable>.toggled[aria-hidden] {
    overflow: hidden;
    visibility: hidden;
    opacity: 0;
    max-height: 0;
    transition: 
        visibility 0s linear .6s,
        opacity .6s ease-in,
        max-height .6s ease-out;
}
.toggled[aria-hidden="true"] {
    max-height: 0 !important; /* Overrides inline style */
}
.toggled[aria-hidden="false"] {
    visibility: visible;
    opacity: 1;
    max-height: 50em; /* Set more accurately inline by JavaScript */
    transition-delay: 0s, 0s, 0s; /* unit "s" is required */
    transition-timing-function: linear, linear, ease-out;
}</code></pre>
        </figure>

        <figure>
          <figcaption>JavaScript</figcaption>
            <pre><code class=language-javascript spellcheck=false contenteditable>const toggler = (() =&gt; {
  
  const dataAttr = "data-toggler";

  // Get height of an element object
  // Assumes it is hidden by max-height: 0 in the CSS
  const getHeight = (obj) =&gt; {
    obj.setAttribute("style", "max-height: auto");
    const height = obj.scrollHeight + "px";
    obj.removeAttribute("style");
    return height;
  };
  
  // Toggles the show/hide state of button and block using ARIA attributes
  const toggleState = (togglerBtn, isHidden) =&gt; {
  
    const toggledAttr = togglerBtn.getAttribute(dataAttr);
    if (!toggledAttr) {return;}
    
    const toggled = document.querySelector(toggledAttr);
    if (!toggled) {return;}

    if (isHidden) { // Show
      toggled.setAttribute("style", "max-height: " + getHeight(toggled));
    } else { // Hide
      toggled.removeAttribute("style");
    }

    togglerBtn.setAttribute("aria-expanded", isHidden);
    toggled.setAttribute("aria-hidden", !isHidden);
  };
  
  const isOpen = (togglerBtn) =&gt; {
    return togglerBtn.getAttribute("aria-expanded") === "true";
  };
  
  const togglerClicked = (e) =&gt; {
    const togglerBtn = e.target;
    toggleState(togglerBtn, !isOpen(togglerBtn));
  };
  
  const initialise = (() =&gt; {

    const togglerButtons = document.querySelectorAll("["+ dataAttr + "]");

    // Run through each toggle button which has a data-toggler3 set
    for (const togglerBtn of togglerButtons) {
      
      // Set ARIA states
      toggleState(togglerBtn, isOpen(togglerBtn));

      // Toggle ARIA state on a button click
      togglerBtn.addEventListener("click", togglerClicked);
    }
  })();
  
})();</code></pre>
        </figure>

    </div>
  </div>

</section>


 

<section>
  
  <div>
    <button class=toggler_3 data-toggler="#toggled_4">
      Toggle a <strong>specified element</strong> using JS (short content)
    </button>
  </div>

  <div class="toggled_3 toggled-short" id=toggled_4>
    <div class=tog_content>
      
      <figure class=tog_fig-solo>
        <figcaption>CSS</figcaption>
        <pre><code class=language-css spellcheck=false contenteditable>.toggled[aria-hidden].toggled-short {
  transition-duration: 0s, .4s, .4s;
}</code></pre>
      </figure>

    </div>
  </div>

</section>


<!--  Footer include -->
[[[https://codepen.io/2kool2/pen/mKeeGM]]]
!

CSS 

              
                /* Generic styles */

*, *::after, *::before {
  box-sizing: inherit;
}
html {
  overflow-y: scroll;
  touch-action: manipulation;
}
body {
  font-family: sans-serif;
  padding: 0 2rem;
  max-width: 50rem;
  margin: 2rem auto;
  text-align: center;
  line-height: 1.5;
  backgound-color: hsl(0, 0%, 35%);
  background-position: center bottom;
  background-size: cover;
  background-attachment: fixed;
  /* Unsplash: Ronald Yang */
  background-image: url(https://images.unsplash.com/photo-1434144893279-2a9fc14e9337?w=1920);
}
h1 {
  font-weight: 100;
  color: #fff;
  text-shadow: 0 0 3px #000;
  background-color: hsla(0, 0%, 35%, 0.9);
  margin: 3rem 0;
  line-height: 1.2;
  padding: 0.25rem;
}
section {
  margin: 3rem 0;
}
ul {
  max-width: 12rem;
  margin: 1rem auto;
}
li {text-align: left}

.tog_title {
  display: block;
  font-size: 1rem;
  font-weight: 100;
  font-style: normal;
  margin: 0;
  text-shadow: 0 0 2px #000;
}
figure {
  position: relative;
  margin: 1rem 0 0;
}
figcaption {
  font-weight: 700;
  padding: 0;
  margin: 0;
  left: 1rem;
  font-size: 1rem;
  letter-spacing: 0.05em;
  text-shadow: 0 1px #000;
}
.smaller,
a {
  color:#fff;
  background-color: hsla(0, 0%, 35%, 0.8);
  padding:.5rem;
  text-shadow: 0 1px #000;
  letter-spacing: 0.05em;
}
.visually-hidden {
  /*https://developer.yahoo.com/blogs/ydn/clip-hidden-content-better-accessibility-53456.html*/
  position: absolute !important;
  clip: rect(1px, 1px, 1px, 1px);
  padding:0 !important;
  border:0 !important;
  height: 1px !important;
  width: 1px !important;
  overflow: hidden;
}
button * {pointer-events:none;}
button::-moz-focus-inner { 
	border: 0; 
	padding: 0; 
	margin-top:-2px; 
	margin-bottom: -2px; 
}
[class^="toggler"] {
  /* Just the button prettiness here */
  font-size: 1.125rem;
  line-height: 1.2;
  display: block;
  box-sizing: border-box;
  width: 100%;
  margin: 0;
  padding: 1rem;
  border: 0 solid;
  background-color: hsl(0, 0%, 80%);
  cursor: pointer;
  transition: all .3s ease-out;
  outline: 0 solid;
  box-shadow: 0 2px 4px rgba(0,0,0,.5);
}
[class^="toggler"]:hover,
[class^="toggler"]:focus {
  background-color: hsl(0, 0%, 90%);
  outline: 0 solid;
  box-shadow: 0 3px 6px rgba(0,0,0,.75);
}
[class^="toggler"]:active {
  box-shadow: inset 0 0 2px rgba(0,0,0,.75);
}
[class^="toggled"] {
  box-shadow: 0 3px 6px rgba(0,0,0,.75);
}
.tog_content {
  background-color: hsla(0, 0%, 35%, 0.8);
  color: #fff;
  display: block;
  padding: 1rem;
}
.tog_fig-solo {
  margin:0
}



 
/* Next Sibling inline JS */

.toggler_1[aria-expanded="false"] + .toggled_1 {
  overflow: hidden;
  visibility: hidden;
  opacity: 0.35;
  max-height: 0;
  transition:
    visibility 0s ease .6s,
    opacity .6s ease-in 0s,
    max-height .6s ease-out 0s;
}
.toggler_1[aria-expanded="true"] + .toggled_1 {
  overflow: hidden;
  visibility: visible;
  opacity: 1;
  /* Note: Manually set, check content visible at minimum viewport widths */
  max-height: 75rem;
  transition:
    visibility 0s ease 0s,
    opacity .6s ease-in 0s,
    max-height 1s ease-out 0s;
}
 


/* Specified element using inline JS*/

.toggled_5[aria-hidden] {
  overflow: hidden;
  visibility: hidden; /* Removes content from keyboard focus chain */
  opacity: 0;
  max-height: 0;
  transition: 
    visibility 0s linear .6s,
    opacity .6s ease-in,
    max-height .6s ease-out;
}
.toggled_5[aria-hidden="true"] {
  max-height: 0 !important; /* Overrides inline style */
}
.toggled_5[aria-hidden="false"] {
  visibility: visible;
  opacity: 1;
  max-height: 50em; /* Set more accurately inline by JavaScript */
  transition-delay: 0s, 0s, 0s;
  transition-timing-function: linear, linear, ease-out;
}


 
 
/* Next sibling without JS */

.tog_container,
.toggler_2,
.toggled_2 {
  display: block;
}
 
.toggled_2 {
  overflow: hidden;
  visibility: hidden;
  opacity: 0.35;
  max-height: 0;
  transition:
    visibility 0s ease .6s,
    opacity .6s ease-in 0s,
    max-height .6s ease-out 0s;
}
:checked + .toggled_2 {
  visibility: visible;
  opacity: 1;
  /* Ensure max-height is sufficient at min-width */
  max-height: 50rem;
  transition-delay: 0s, 0s, 0s; /* unit "s" is required */
}
 



/* Specified element using unobtrusive JS */
 
.toggled_3[aria-hidden] {
  overflow: hidden;
  visibility: hidden;
  opacity: 0;
  max-height: 0;
  transition: 
    visibility 0s linear .6s,
    opacity .6s ease-in,
    max-height .6s ease-out;
}
.toggled_3[aria-hidden="true"] {
    max-height: 0 !important; /* Overrides inline style */
}
.toggled_3[aria-hidden="false"] {
    visibility: visible;
    opacity: 1;
    max-height: 50em; /* Set more accurately inline by JavaScript */
    transition-delay: 0s, 0s, 0s; /* unit "s" is required */
    transition-timing-function: linear, linear, ease-out;
}


/* Specified element, short content addition */

[class^="toggled"][aria-hidden].toggled-short {
  transition-duration: 0s, .4s, .4s;
}


/* Specified element, extra long content addition */

.toggled-long[aria-hidden="true"] { /* Closing */
  transition-duration: 0s, .6s, .6s;
  transition-delay: 0.8s, 0s, 0s; /* unit "s" is required */
}
.toggled-long[aria-hidden="false"] { /* Opening */
  transition-duration: 0s, .8s, .8s;
  transition-delay: 0s, 0s, 0s; /* unit "s" is required */
}






/* Prism - is used for code highlighting from an external pen: https://codepen.io/2kool2/pen/MEbeEg */
!

JS 

              
                // JS is needed to toggle an object which isn't a sibling.

const toggler = (() => {
  
  const dataAttr = "data-toggler";


	// Get height of an element object
  // Assumes it is hidden by max-height: 0 in the CSS
	const getHeight = (obj) => {
    obj.setAttribute("style", "max-height: auto");
		const height = obj.scrollHeight + "px";
    obj.removeAttribute("style");
		return height;
	};
  

  // Toggles the show/hide state of button and block using ARIA attributes
  const toggleState = (togglerBtn, isHidden) => {
  
    const toggledAttr = togglerBtn.getAttribute(dataAttr);
    if (!toggledAttr) {return;}
    
    const toggled = document.querySelector(toggledAttr);
    if (!toggled) {return;}

    if (isHidden) { // Show
      //toggled.setAttribute("style", "max-height: " + getHeight(toggled));
      toggled.setAttribute('style', 'max-height:' + toggled.scrollHeight + 'px');
    } else { // Hide
      //toggled.removeAttribute("style");
    }

    togglerBtn.setAttribute("aria-expanded", isHidden);
    toggled.setAttribute("aria-hidden", !isHidden);
  };
  

  const isOpen = (togglerBtn) => {
    return togglerBtn.getAttribute("aria-expanded") === "true";
  };
  

  const togglerClicked = (e) => {
    const togglerBtn = e.target;
    toggleState(togglerBtn, !isOpen(togglerBtn));
  };
  

  const initialise = (() => {

    const togglerButtons = document.querySelectorAll("["+ dataAttr + "]");

    // Run through each toggle button which has a data-toggler3 set
    for (const togglerBtn of togglerButtons) {
      
      // Set ARIA states
      toggleState(togglerBtn, isOpen(togglerBtn));

      // Toggle ARIA state on a button click
      togglerBtn.addEventListener("click", togglerClicked);
    }
  })();
  
})();





/* Prism - is used for code highlighting from an external pen: https://codepen.io/2kool2/pen/MEbeEg */
!
999px

Console