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HTML

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Insecure Resource

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CSS

About CSS Preprocessors

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

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

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HTML 

              
                <div class="qna">
  <button class="accordion">Question 1</button>
  <div class="panel panel-closed">
    <p>Answer of Question 1</p>
  </div>
  <button class="accordion">Question 2</button>
  <div class="panel panel-closed">
    <p>Answer of Question 2</p>
  </div>
  <button class="accordion">Question 3</button>
  <div class="panel panel-closed">
    <p>Answer of Question 3</p>
  </div>
  <button class="accordion">Question 4</button>
  <div class="panel panel-closed">
    <p>Answer of Question 4</p>
  </div>
</div>
!

CSS 

              
                /* Centers horizontally */
.qna{
  max-width: 500px;
  margin: 0 auto;
}
/* Button default resets */
button{
  border: none;
  outline: none;
  cursor: pointer;
}
/* Styling the accordion buttons */
.accordion{
  width: 100%;
  background-color: #303030;
  color: #fff;
  font-size: 20px;
  padding: 18px 20px;
  margin-bottom: 1px;
  text-align: left;
  /*  To push the plus sign to the right  */
  display: flex;
  justify-content: space-between;
  align-items: center;
}
/* adding the "plus" sign (+) */ 
.accordion::after{
  content: '\02795';
  font-size: 20px;
  color: #fff;
}
.panel{
  background-color: #303030;
  color: #fff;
  margin-bottom: 4px;
  overflow: hidden;
  transition: max-height .33s cubic-bezier(.5,0,.1,1);
}
.panel > p {
  font-size: 20px;
  padding: 10px 20px;
}
.panel-closed{
  max-height: 0;
  overflow: hidden;
}
.panel-open{
  max-height: 700px;
}
/* active class for accordion, adds the "cross sign (x)" */
.accordion-active::after {
  content: "\274C";
}
!

JS 

              
                let accordion = document.getElementsByClassName("accordion");
const totalAccordions = accordion.length;

for (let i = 0; i < totalAccordions; i++) {
  accordion[i].addEventListener("click", (e) => {
    let panel = e.target.nextElementSibling;
   
    if (panel.classList[1] === "panel-closed") {
      e.target.classList.toggle("accordion-active");
      panel.classList.toggle("panel-open");
      closeAllExcept(panel);
    }
  });
} 

const closeAllExcept = (pan) => {
  for (let i = 0; i < totalAccordions; i++) {
    let panelToClose = accordion[i].nextElementSibling;
    if(panelToClose !== pan){
       accordion[i].classList.remove("accordion-active");
       panelToClose.classList.remove("panel-open");
    }
  }
}
!
999px

Console