PDF.js Previous/Next example

by Craig Martin

HTML

<script src="//mozilla.github.io/pdf.js/build/pdf.js"></script>
<div>
  <button id="pprev">Previous</button>
  <button id="pnext">Next</button>
  &nbsp; &nbsp;
  <span>Page: <span id="page_num"></span> / <span id="page_count"></span></span>
  &nbsp; &nbsp;
<button id="zoom">Zoom In</button>
<button id="zoomout">Zoom Out</button>
</div>
<canvas id="the-canvas" style="direction: ltr;pointer-events: none;"></canvas>

JavaScript

// Loaded via <script> tag, create shortcut to access PDF.js exports.
var pdfjsLib = window['pdfjs-dist/build/pdf'];

// The workerSrc property shall be specified.
pdfjsLib.GlobalWorkerOptions.workerSrc = '//mozilla.github.io/pdf.js/build/pdf.worker.js';

var pdfDoc = null,
    pageNum = 1,
    pageRendering = false,
    pageNumPending = null,
    scale = 0.9,
    canvas = document.getElementById('the-canvas'),
    ctx = canvas.getContext('2d');

/**
 * Get page info from document, resize canvas accordingly, and render page.
 * @param num Page number.
 */
function renderPage(num, zoom) {
  pageRendering = true;
  // Using promise to fetch the page
  pdfDoc.getPage(num).then(function(page) {
    var viewport = page.getViewport({scale: zoom});
    canvas.height = viewport.height;
    canvas.width = viewport.width;

    // Render PDF page into canvas context
    var renderContext = {
      canvasContext: ctx,
      viewport: viewport
    };
    var renderTask = page.render(renderContext);

    // Wait for rendering to finish
    renderTask.promise.then(function() {
      pageRendering = false;
      if (pageNumPending !== null) {
        // New page rendering is pending
        renderPage(pageNumPending, 1);
        pageNumPending = null;
      }
    });
  });

  // Update page counters
  document.getElementById('page_num').textContent = num;
}

/**
 * If another page rendering in progress, waits until the rendering is
 * finised. Otherwise, executes rendering immediately.
 */
window.queueRenderPage = function queueRenderPage(num, zoom) {
  if (pageRendering) {
    pageNumPending = num;
    scale = zoom;
  } else {
    renderPage(num, zoom);
  }
}

/**
 * Displays previous page.
 */
window.onPrevPage = function() {
  if (pageNum <= 1) {
    return;
  }
  pageNum--;
  queueRenderPage(pageNum, 1);
}
document.getElementById('pprev').addEventListener('click', onPrevPage);

/**
 * Displays next page.
 */
window.onNextPage = function() {
  if (pageNum >= pdfDoc.numPages)...