CodePen Embed - Assessment - JavaScript building blocks

<html lang="en-us">
  <head>
    <meta charset="utf-8">

    <title>Image gallery</title>

    <link rel="stylesheet" href="style.css">
    
  </head>

  <body>
    <h1>Image gallery example</h1>

    <div class="full-img">
      <img class="displayed-img" src="https://cdn.glitch.global/3efa4dc0-c1aa-4ccc-a660-baa79fe0f8ec/pic1.jpg?v=1662647926542" alt="Closeup of a human eye">
      <div class="overlay"></div>
      <button class="dark">Darken</button>
    </div>

    <div class="thumb-bar">


    </div>
    <script src="main.js"></script>
  </body>
</html>

h1 {
  font-family: helvetica, arial, sans-serif;
  text-align: center;
}

body {
  width: 640px;
  margin: 0 auto;
}

.full-img {
  position: relative;
  display: block;
  width: 640px;
  height: 480px;
}

.overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 640px;
  height: 480px;
  background-color: rgba(0,0,0,0);
}

button {
  border: 0;
  background: rgba(150,150,150,0.6);
  text-shadow: 1px 1px 1px white;
  border: 1px solid #999;
  position: absolute;
  cursor: pointer;
  top: 2px;
  left: 2px;
}

.thumb-bar img {
  display: block;
  width: 20%;
  float: left;
  cursor: pointer;
}

const displayedImage = document.querySelector('.displayed-img');
const thumbBar = document.querySelector('.thumb-bar');

const btn = document.querySelector('button');
const overlay = document.querySelector('.overlay');

/* Declaring the array of image filenames */
const images = ['pic1.jpg', 'pic2.jpg', 'pic3.jpg', 'pic4.jpg', 'pic5.jpg'];

/* Declaring the alternative text for each image file */
// How was I supposed to use this???

/* Looping through images */
for (const image of images) {
    const newImage = document.createElement('img');
    newImage.setAttribute('src', 'xxx');
    newImage.setAttribute('alt', 'xxx');
    thumbBar.appendChild(newImage);
    switch (image) {
        case 'pic1.jpg':
            newImage.src = 'https://cdn.glitch.global/3efa4dc0-c1aa-4ccc-a660-baa79fe0f8ec/pic1.jpg?v=1662647926542';
            newImage.alt = 'Closeup of a human eye';
            break;
        case 'pic2.jpg':
            newImage.src = 'https://cdn.glitch.global/3efa4dc0-c1aa-4ccc-a660-baa79fe0f8ec/pic2.jpg?v=1662647931322';
            newImage.alt = 'Wavy surface';
            break;
        case 'pic3.jpg':
            newImage.src = 'https://cdn.glitch.global/3efa4dc0-c1aa-4ccc-a660-baa79fe0f8ec/pic3.jpg?v=1662647935495';
            newImage.alt = 'Purple flowers';
            break;
        case 'pic4.jpg':
            newImage.src = 'https://cdn.glitch.global/3efa4dc0-c1aa-4ccc-a660-baa79fe0f8ec/pic4.jpg?v=1662647939623';
            newImage.alt = 'Ancient art on a wall';
            break;
        case 'pic5.jpg':
            newImage.src = 'https://cdn.glitch.global/3efa4dc0-c1aa-4ccc-a660-baa79fe0f8ec/pic5.jpg?v=1662647943671';
            newImage.alt = 'A butterfly on a leaf';
            break;
    }; 
    
    thumbBar.addEventListener('click', (event)=> {
        const currentSrc = event.target.getAttribute('src');
        const currentAlt = event.target.getAttribute('alt');
        displayedImage.setAttribute('src', currentSrc);
        displayedImage.setAttribute('alt', currentAlt);
    });
}

/* Wiring up the Darken/Lighten button */
btn.addEventListener('click', () => {
    if (btn.getAttribute('class') === 'dark') {
        btn.setAttribute('class', 'light');
        btn.textContent = 'Lighten';
        overlay.style.backgroundColor = 'rgba(0,0,0,0.5)';
    } else {
        btn.setAttribute('class','dark');
        btn.textContent = 'Darken';
        overlay.style.backgroundColor = 'rgba(0,0,0,0)';
    }
})

/* NOTE for myself
- I forgot to put const in for...of () so it didn't work.
- I didn't put quote marks at "case 'picx.jpg':" so the photos weren't displayed on thumbBar. 
- It took a while but I could figure out how to add click event handler only to thumbBar!
  To get the src and alt of the 'current image', target "event.target" so it targets innermost element.
*/

/* Alternative src & alt Switch
    switch (image) {
        case 'pic1.jpg': 
            newImage.setAttribute('src','images/pic1.jpg');
            newImage.setAttribute('alt', 'Closeup of a human eye');
            thumbBar.appendChild(newImage);
            break;
        case 'pic2.jpg':
            newImage.setAttribute('src','images/pic2.jpg');
            newImage.setAttribute('alt','Wavy surface');
            thumbBar.appendChild(newImage); 
            break;
        case 'pic3.jpg':
            newImage.setAttribute('src','images/pic3.jpg');
            newImage.setAttribute('alt','Purple flowers');
            thumbBar.appendChild(newImage); 
            break;
        case 'pic4.jpg':
            newImage.setAttribute('src','images/pic4.jpg');
            newImage.setAttribute('alt','Ancient art on a wall');
            thumbBar.appendChild(newImage); 
            break;
        case 'pic5.jpg':
            newImage.setAttribute('src','images/pic5.jpg');
            newImage.setAttribute('alt','A butterfly on a leaf');
            thumbBar.appendChild(newImage); 
            break;
    }; 
*/

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