DP
Collection tracker with HTML, CSS, JS

How to make a simple collection tracker with HTML, CSS and JavaScript

After figuring out different approaches to making a collection tracker application, I have decided to create a simplified version with just HTML, CSS and JavaScript. Here is the final code with a few adjustments.

HTML structure (index.html)

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Collection Tracker</title>
    <link rel="stylesheet" href="styles.css" />
  </head>
  <body>
    <header>
      <h1>Collection Tracker</h1>
      <div class="actions">
        <button id="add-item-btn">Add item</button>
        <label class="import-label">
          Import JSON
          <input
            type="file"
            id="import-file-input"
            accept=".json,application/json"
            hidden
          />
        </label>
        <button id="export-btn">Export JSON</button>
      </div>
    </header>
    <main>
      <table id="items-table">
        <thead>
          <tr>
            <th>#</th>
            <th>Date</th>
            <th>Gifted by</th>
            <th>Origin</th>
            <th>Description</th>
          </tr>
        </thead>
        <tbody id="items-tbody">
          <!-- Table contents generated by JS -->
        </tbody>
      </table>
    </main>
    <!-- Modal -->
    <div id="modal-overlay" class="modal-overlay hidden">
      <div class="modal">
        <h2>Add new item</h2>
        <form id="add-item-form">
          <label>
            Number
            <input type="number" name="number" required />
          </label>
          <label>
            Date
            <input type="date" name="date" />
          </label>
          <label>
            Gifted by
            <input type="text" name="giftedBy" />
          </label>
          <label>
            Origin
            <input type="text" name="origin" />
          </label>
          <label>
            Description
            <textarea name="description"></textarea>
          </label>
          <div class="modal-actions">
            <button type="submit">Save</button>
            <button type="button" id="cancel-modal-btn">Cancel</button>
          </div>
        </form>
      </div>
    </div>
    <script src="app.js"></script>
  </body>
</html>

Functionality (app.js)

let items = [];

const tbody = document.getElementById("items-tbody");
const addItemBtn = document.getElementById("add-item-btn");
const modalOverlay = document.getElementById("modal-overlay");
const addItemForm = document.getElementById("add-item-form");
const cancelModalBtn = document.getElementById("cancel-modal-btn");
const importFileInput = document.getElementById("import-file-input");
const exportBtn = document.getElementById("export-btn");

function renderItems() {
  tbody.innerHTML = "";
  items.forEach((item) => {
    const tr = document.createElement("tr");
    tr.innerHTML = `
      <td>${item.number ?? ""}</td>
      <td>${item.date ?? ""}</td>
      <td>${item.giftedBy ?? ""}</td>
      <td>${item.origin ?? ""}</td>
      <td>${item.description ?? ""}</td>
    `;
    tbody.appendChild(tr);
  });
}

function openModal() {
  modalOverlay.classList.remove("hidden");
}

function closeModal() {
  modalOverlay.classList.add("hidden");
  addItemForm.reset();
}

addItemForm.addEventListener("submit", (e) => {
  e.preventDefault();
  const formData = new FormData(addItemForm);

  const newItem = {
    number: formData.get("number"),
    date: formData.get("date"),
    giftedBy: formData.get("giftedBy"),
    origin: formData.get("origin"),
    description: formData.get("description"),
  };

  items.push(newItem);
  renderItems();
  closeModal();
});

importFileInput.addEventListener("change", (e) => {
  const file = e.target.files[0];
  if (!file) return;

  const reader = new FileReader();
  reader.onload = (event) => {
    try {
      const text = event.target.result;
      const parsed = JSON.parse(text);
      if (!Array.isArray(parsed)) {
        alert("Imported JSON is not an array.");
        return;
      }
      items = parsed;
      renderItems();
    } catch (err) {
      console.error("Import error:", err);
      alert("Could not import data from this file. Ensure it is valid JSON.");
    } finally {
      importFileInput.value = "";
    }
  };
  reader.readAsText(file);
});

exportBtn.addEventListener("click", () => {
  const json = JSON.stringify(items, null, 2);
  const blob = new Blob([json], { type: "application/json;charset=utf-8" });
  const url = URL.createObjectURL(blob);

  const a = document.createElement("a");
  a.href = url;
  a.download = "collection.json";
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);

  URL.revokeObjectURL(url);
});

addItemBtn.addEventListener("click", openModal);
cancelModalBtn.addEventListener("click", closeModal);

renderItems();

Basic styling (styles.css)

body {
  font-family: system-ui, sans-serif;
  margin: 0;
  padding: 0;
  background: #f4f4f5;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 1.5rem;
  background: #18181b;
  color: #f9fafb;
}

h1 {
  margin: 0;
  font-size: 1.25rem;
}

.actions {
  display: flex;
  gap: 0.5rem;
}

button,
.import-label {
  background: #4f46e5;
  color: #f9fafb;
  border: none;
  border-radius: 0.25rem;
  padding: 0.4rem 0.7rem;
  font-size: 0.9rem;
  cursor: pointer;
}

button:hover,
.import-label:hover {
  background: #4338ca;
}

.import-label {
  display: inline-flex;
  align-items: center;
}

main {
  padding: 1rem 1.5rem;
}

table {
  width: 100%;
  border-collapse: collapse;
  background: #ffffff;
  border-radius: 0.25rem;
  overflow: hidden;
}

th,
td {
  padding: 0.5rem;
  border-bottom: 1px solid #e5e7eb;
  font-size: 0.9rem;
}

th {
  text-align: left;
  background: #f3f4f6;
}

.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.6);
  display: flex;
  align-items: center;
  justify-content: center;
}

.modal-overlay.hidden {
  display: none;
}

.modal {
  background: #ffffff;
  padding: 1rem 1.25rem;
  border-radius: 0.5rem;
  width: 320px;
  max-width: 90vw;
  box-shadow: 0 10px 25px rgba(15, 23, 42, 0.25);
}

.modal h2 {
  margin-top: 0;
  margin-bottom: 0.75rem;
}

.modal label {
  display: block;
  margin-bottom: 0.5rem;
  font-size: 0.85rem;
}

.modal input,
.modal textarea {
  width: 100%;
  padding: 0.3rem;
  margin-top: 0.15rem;
  margin-bottom: 0.25rem;
  font-size: 0.85rem;
  border: 1px solid #d4d4d8;
  border-radius: 0.25rem;
}

.modal textarea {
  resize: vertical;
  min-height: 60px;
}

.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 0.5rem;
  margin-top: 0.5rem;
}

If you want to get more details about making this collection tracker, check this post on my Medium blog.

Thank you for reading.

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