Core Concepts

This page explains what pdf2image does to the page when it loads, and how that decides when you can call convert().

Dependencies Injected on Load

pdf2image does not bundle pdf.js or JSZip. As soon as the script runs, it inserts these elements into <head>:

The dependency versions are hard-coded in the source and cannot be swapped through options. The stylesheet always comes from @latest, regardless of the package version you load.

When to Call

Dynamically inserted <script> elements execute asynchronously, so whether pdfjsLib exists right after the package loads depends on cache and network timing. When it does not, convert() rejects with a ReferenceError (pdfjsLib is not defined). By the window load event, every injected script has executed, so wait for it before converting.

<pre id="out"></pre>
<script>
  console.log("immediately:", typeof pdfjsLib, typeof JSZip);
  addEventListener("load", () => {
    console.log("after load:", typeof pdfjsLib, typeof JSZip);
    const injected = [...document.head.querySelectorAll("script[src], link[href]")]
      .map(el => el.src || el.href)
      .filter(url => !url.includes("@pardnchiu/pdf2image@") || url.endsWith(".css"));
    document.getElementById("out").textContent = injected.join("\n");
  });
</script>

The Global Class

Both the UMD and ESM builds set window.pdf2image; the ESM build only adds export const pdf2image = window.pdf2image to export the same class. Each instance holds its own file, type, scale, filename, and conversion results, with no state shared across instances.

Runtime Constraints

Related Pages

• Conversion
• Architecture