使用 PDF.js 异步加载多个 pdf 文件时获取总页数

Question

i´m using pdfjs to load and merge some pdf files. I know how to show page number of a pdf document, but while merging files, i´d like to show a page number based on total pages of all pdf docs. But because it's asynchronous, just using and increment a counter variable is not working.

var actual_page = 1;

(async function loop() {
for (url_item of urls) {
    var loadingTask = pdfjsLib.getDocument(url_item);
        await loadingTask.promise.then(function (pdf) {
            let i = 1;
            while (i <= pdf.numPages) {
                var pageNumber = i;
                pdf.getPage(pageNumber).then(function (page) {
                    //render pdf and print actual_page++ 
                });
            }
        }
    }
}

First page show 1, second page show 3, and 2 will appear on page 10 and so it goes.

Thanks in advance.

Answer 1

I think you're going to need Promise.all or some equivalent to get the pages from getPage in the correct order. That might just make your page numbering thing work.

var pagePromises = [];

while (i <= pdf.numPages) {
    pagePromises.push(pdf.getPage(i));
    i++;
}

Promise.all(pagePromises).then(function (allPages) {
  allPages.forEach(page => {
    // render pdf and print actual_page++
  });
});

});