如何使用pdf.js从pdf正确提取文本 [英] How to correctly extract text from a pdf using pdf.js

问题描述

我是ES6和Promise的新手.我正在尝试pdf.js将pdf文件所有页面中的文本提取到字符串数组中.当提取完成后，我想以某种方式解析数组.说pdf文件(正确通过typedarray传递)有4页，我的代码是:

I'm new to ES6 and Promise. I'm trying pdf.js to extract texts from all pages of a pdf file into a string array. And when extraction is done, I want to parse the array somehow. Say pdf file(passed via typedarray correctly) has 4 pages and my code is:

let str = [];
PDFJS.getDocument(typedarray).then(function(pdf) {
  for(let i = 1; i <= pdf.numPages; i++) {
    pdf.getPage(i).then(function(page) {
      page.getTextContent().then(function(textContent) {
        for(let j = 0; j < textContent.items.length; j++) {
          str.push(textContent.items[j].str);
        }
        parse(str);
      });
    });
  }
});

它可以正常工作，但是，当然，问题是我的parse函数被调用了4次.我只想在完成所有4页提取后才调用parse.

It manages to work, but, of course, the problem is my parse function is called 4 times. I just want to call parse only after all 4-pages-extraction is done.

推荐答案

类似于 https://stackoverflow.com/a/40494019 /1765767 -使用Promise.all收集页面承诺，不要忘记链接当时的页面:

Similar to https://stackoverflow.com/a/40494019/1765767 -- collect page promises using Promise.all and don't forget to chain then's:

function gettext(pdfUrl){
  var pdf = PDFJS.getDocument(pdfUrl);
  return pdf.then(function(pdf) { // get all pages text
    var maxPages = pdf.pdfInfo.numPages;
    var countPromises = []; // collecting all page promises
    for (var j = 1; j <= maxPages; j++) {
      var page = pdf.getPage(j);

      var txt = "";
      countPromises.push(page.then(function(page) { // add page promise
        var textContent = page.getTextContent();
        return textContent.then(function(text){ // return content promise
          return text.items.map(function (s) { return s.str; }).join(''); // value page text 
        });
      }));
    }
    // Wait for all pages and join text
    return Promise.all(countPromises).then(function (texts) {
      return texts.join('');
    });
  });
}

// waiting on gettext to finish completion, or error
gettext("https://cdn.mozilla.net/pdfjs/tracemonkey.pdf").then(function (text) {
  alert('parse ' + text);
}, 
function (reason) {
  console.error(reason);
});

<script src="https://npmcdn.com/pdfjs-dist/build/pdf.js"></script>

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