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About the <head>

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CSS

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CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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About CSS Base

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Babel includes JSX processing.

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HTML 

              
                <!DOCTYPE html>
<html lang="en">
<!-- Design by foolishdeveloper.com -->
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style media="screen">
    @import url('https://fonts.googleapis.com/css?family=Montserrat');

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  font-family: 'Montserrat', sans-serif;
  background-color: #0f5086;
  color: #fff;
  margin-top: 100px;
}

.accordion {
  width: 90%;
  max-width: 1000px;
  margin: 2rem auto;
}
.accordion-item {
  background-color: #fff;
  color: #111;
  margin: 1rem 0;
  border-radius: 0.3rem;
  box-shadow: 0 2px 5px 0 rgba(0,0,0,0.25);
}
.accordion-item-header {
  padding: 0.5rem 3rem 0.5rem 1rem;
  min-height: 3.5rem;
  line-height: 1.25rem;
  font-weight: bold;
  display: flex;
  font-size: 17px;
  align-items: center;
  position: relative;
  cursor: pointer;
}
.accordion-item-header::after {
  content: "\002B";
  font-size: 2rem;
  position: absolute;
  right: 1rem;
}
.accordion-item-header.active::after {
  content: "\2212";
}
.accordion-item-body {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.2s ease-out;
}
.accordion-item-body-content {
  padding: 1rem;
  line-height: 1.5rem;
  font-family: sans-serif;
  border-top: 1px solid;
  font-size: 16px;
  border-image: linear-gradient(to right, transparent, #34495e, transparent) 1;
}

@media(max-width:767px) {
  html {
    font-size: 14px;
  }
}
  </style>
</head>
<body>


<div class="accordion">
  <div class="accordion-item">
    <div class="accordion-item-header">
      Accordion Menu Using HTML
    </div>
    <div class="accordion-item-body">
      <div class="accordion-item-body-content">
        Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ipsa excepturi incidunt dicta quasi porro, magnam aliquid, itaque rerum quos repellendus sapiente nemo culpa molestias officiis?
      </div>
    </div>
  </div>
  <div class="accordion-item">
    <div class="accordion-item-header">
      Accordion Using Pure CSS
    </div>
    <div class="accordion-item-body">
      <div class="accordion-item-body-content">
        Lorem ipsum dolor sit amet, consectetur adipisicing elit. Fugiat repellat maiores veritatis et, dicta necessitatibus quas illo commodi libero!<br>
        Lorem ipsum dolor sit amet, consectetur adipisicing elit. Recusandae sequi a fugit totam tempore,  aspernatur.
      </div>
    </div>
  </div>
  <div class="accordion-item">
    <div class="accordion-item-header">
      Accordion Menu using Javascript
    </div>
    <div class="accordion-item-body">
      <div class="accordion-item-body-content">
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ducimus alias dolorum itaque incidunt amet animi explicabo facilis, voluptates, maxime repudiandae minus at, voluptatibus optio facere in obcaecati exercitationem, ab quod.
      </div>
    </div>
  </div>
  <div class="accordion-item">
    <div class="accordion-item-header">
      Accordion Bar With Jquery
    </div>
    <div class="accordion-item-body">
      <div class="accordion-item-body-content">
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quibusdam error alias, incidunt dolor aperiam soluta aspernatur tenetur eaque, iusto consequuntur sit nam labore id suscipit. Soluta quos, molestias cum ab laborum odit quaerat quibusdam.
      </div>
    </div>
  </div>
  <div class="accordion-item">
    <div class="accordion-item-header">
      Accordion Bar using Bootstrap 5
    </div>
    <div class="accordion-item-body">
      <div class="accordion-item-body-content">
        CORS, aka Cross-Origin Resource Sharing, is a mechanism that enables many resources (e.g. images, stylesheets, scripts, fonts) on a web page to be requested from another domain outside the domain from which the resource originated.
      </div>
    </div>
  </div>
</div>
<script type="text/javascript">
const accordionItemHeaders = document.querySelectorAll(".accordion-item-header");

accordionItemHeaders.forEach(accordionItemHeader => {
  accordionItemHeader.addEventListener("click", event => {



    accordionItemHeader.classList.toggle("active");
    const accordionItemBody = accordionItemHeader.nextElementSibling;
    if(accordionItemHeader.classList.contains("active")) {
      accordionItemBody.style.maxHeight = accordionItemBody.scrollHeight + "px";
    }
    else {
      accordionItemBody.style.maxHeight = 0;
    }

  });
});
</script>
</body>
</html>
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