var url = "./doc.pdf?v=<?php echo date('YmdHis'); ?>" + new Date().getTime();

var pdfjsLib = window["pdfjs-dist/build/pdf"];
pdfjsLib.GlobalWorkerOptions.workerSrc = "https://cdnjs.cloudflare.com/ajax/libs/pdf.js/2.2.2/pdf.worker.js";

var pdfDoc = null,
    pageNum = 1,
    pageRendering = false,
    pageNumPending = null,
    scale = 1.5;

function renderPage(num, canvas) {
    var ctx = canvas.getContext("2d");
    pageRendering = true;
    // Using promise to fetch the page
    pdfDoc.getPage(num).then(function (page) {
        var viewport = page.getViewport({ scale: scale });
        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);
                pageNumPending = null;
            }
        });
    });
}

pdfjsLib.getDocument(url).promise.then(function (pdfDoc_) {
    pdfDoc = pdfDoc_;

    const pages = parseInt(pdfDoc.numPages);

    var canvasHtml = "";
    for (var i = 0; i < pages; i++) {
        canvasHtml += '<canvas id="canvas_' + i + '"></canvas>';
    }

    document.getElementById("canvases").innerHTML = canvasHtml;

    for (var i = 0; i < pages; i++) {
        var canvas = document.getElementById("canvas_" + i);
        renderPage(i + 1, canvas);
    }
});