The generation of unique worm images is achieved by using a Set called generatedWorms to keep track of the combinations that have been generated. Here's how it works: 

• At the beginning of the script, an empty Set is created like this:

const generatedWorms = new Set();

• This Set will be used to store the combinations of worm images that have been generated.

• Generating Unique Worms: When the user clicks the "Generate Image" button, the generateImage function is called. Inside this function, it enters a loop that continues until a unique worm combination is found:

while (!uniqueWormFound) {

  // ...

}

• Inside this loop, random images are selected for each part of the worm (background, body, eye, mouth, headgear), and a combination string is created using these random images:

const wormCombination = `${randomBackground}-${randomBody}-${randomEye}-${randomMouth}-${randomHeadgear}`;

• Checking for Uniqueness: Before adding the combination to the generatedWorms set, it checks whether this combination has already been generated:

if (!generatedWorms.has(wormCombination)) {

  // This combination is unique

  // Add it to the set

  generatedWorms.add(wormCombination);

  uniqueWormFound = true; // Exit the loop

  // ...

}

• If the combination has not been generated before, it's considered unique, added to the set, and the loop exits. If it has been generated before, the loop continues until a unique combination is found.

• Keeping Track: The generatedWorms set keeps track of all unique combinations of worm images that have been generated during the user's session. It prevents duplicates by checking if a newly generated combination is already in the set.

• Exporting Images: When the user clicks the "Export as SVG" button, the script will serialize the entire SVG container, including all the layers of the currently displayed worm images. It doesn't regenerate a new worm; instead, it exports the existing one that has been generated and displayed in the SVG container.

• Persistence: The generatedWorms set persists as long as the user stays on the page. It holds the unique worm combinations in memory, allowing the code to ensure that the same combination isn't generated again during the same session.

So, essentially, the script keeps track of generated worm combinations using the Set data structure, ensuring that they are unique until the user leaves or refreshes the page.