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HTML

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CSS

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CSS Base

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <div class="container">
<h1>Responsive Image</h1>
  <div class="flexContainer">
    <div><p>The image to the right is inside a flex item inside a flex container <code>.flexContainer</code></p>
      <p>As the flex container is resized the image resizes.  This is due to the <code>width</code> of 100% set by <code>.respImg</code> class.</p>
      <p>The 100% is relative, ie it is 100% of its parent's width.</p>
      <p>In this case the parent of the &lt;img&gt; is the flex-item, that itself is given 50% of the flex container via the flex property of <code>flex:0 0 50%</code>.</p>
    </div>
  <img src="https://picsum.photos/400/300" alt="Placeholder 400x100" class="respImg">
    </div>
</div>
</div>
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CSS 

              
                /* Utility class for responsive images */
.respImg{
  width:100%;
  height:auto;
}
/* Default mobile-first styles */
body {
    font-family: 'Arial', sans-serif;
    font-size: 1rem;
    color: #333;
}
.container{
  width:100%;
/*   exaggerated borders to illustrate demo */
  border-left:5px solid #000;
  border-right:5px solid #000;
  padding:5px;
}
.flexContainer{
  display:flex;
  gap:10px;
}
/* Give both flex items 50% of the flex space */
.flexContainer > div{
  flex:0 0 50%;
}
/* Tablet styles */
@media (min-width: 600px) {
    body {
        font-size: 1.1rem;
    }
    .container{
        width:100%;
    }
}

/* Desktop styles */
@media (min-width: 1024px) {
    body {
        font-size: 1.2rem;

    }
    .container{
        max-width: 960px;
        margin: auto;
    }
}
code{
color: #ed143d;
    background-color: #fff;
    padding-left: 5px;
    padding-right: 5px;
    font-family: Consolas, "Andale Mono", "Lucida Console", "Lucida Sans Typewriter", Monaco, "Courier New", "monospace";
}
!

JS
!
999px

Console