以JSON格式格式化目录中的文件列表

Question

I am required to list all files in a directory in JSON format which will be passed on to jade template. How can I do that asynchronously?

router.get('/', function(req, res, next) {
  res.render('index', {
    title: 'Advanced Solution Writer',
    pdf: JSON.parse( /*need to get all files inside directory foo*/)});

});

Can I write something like anonymous function that returns list of files in it? Here is a piece of code that I tried which is not working. I am new to node.js

router.get('/', function(req, res, next) {
  res.render('index', {
    title: 'Advanced Solution Writer',
    pdf: JSON.parse(

        function() {
          const fs = require('fs');
          fs.readdir("./public/pdf", function (err, files) {
            if (err) {
              console.log(err);
            }
            return files;
          })
        }
    )});

});

Answer 1

use res.render inside the readdir callback:

var fs = require('fs');

router.get('/', function(req, res, next) {
    fs.readdir("./public/pdf", function(err, files) {
      if (err) {
        console.log(err);
      }

      res.render('index', {
         title: 'Advanced Solution Writer',
         pdf: JSON.parse(files)
      });
   });
});

Answer 2

You're doing it inside out. The asynchronous approach requires you to start by reading the file list, and in the callback, you can render the page.

Roughly like this:

const fs = require('fs');

router.get('/', function(req, res, next) {
  fs.readdir("./public/pdf", function (err, files) {
    if (err) {
      console.error(err);
      throw err; // To generate a 500 internal server error
    }
    res.render('index', {
      title: 'Advanced Solution Writer',
      pdf: JSON.parse(files)
    });
  });
});

I also recommend looking into Promises as an alternative to callbacks. Promises can make the flow of your code clearer and simpler.