如何返回此对象，而不是记录它？

Question

I have a static site generator for which I want to list all available partials in the templates/partials folder. I need to format the list of partials as the following kind of object:

var partials = {
  'header': 'partials/header', // from './templates/partials/header.html'
  'footer': 'partials/footer' // from './templates/partials/footer.html'
};

I've followed this example to put together this node script:

'use strict';

/**
 * Dependencies
 */

var fs = require("fs");
var path = require("path");
var p = 'templates/partials';

/**
 * Scan folder and return object with partials
 */

fs.readdir(p, function (err, files) {
  var obj = {};

  if (err) {
    throw err;
  };

  for (var i = 0; i < files.length; i++) {
    obj[path.basename(files[i], '.html')] = 'partials/' + files[i];
  };

  console.log(obj);
});

When executed from the root of the project it logs:

{ footer: 'partials/footer.html',
  header: 'partials/header.html' }

Which is good, but I want to return it, not log it. Also I get the idea that what I've written is rather clunky. So my question is, how do I return the object, and how do I make this more robust?

Answer 1

You should provide a callback function:

function readfiles(callback) {
  fs.readdir(p, function (err, files) {
    var obj = {};

    if (err) {
      throw err;
    };

    for (var i = 0; i < files.length; i++) {
      obj[path.basename(files[i], '.html')] = 'partials/' + files[i];
    };

    callback(obj);
  });
}

This would be used as follows:

readfiles(function(files) {
  // Do stuff with files here.
});

Callback functions allow IO to be done asynchronously; this often provides a large speedup to code because it does not need to wait for IO to finish. In this case, it is not so useful, but the callback pattern is very common in Node.js and so it's good practice to use it here to.

Answer 2

var results = fs.readdir(p, function(err, files) {
  var obj = {};

  if (err) {
    throw err;
  };

  for (var i = 0; i < files.length; i++) {
    obj[path.basename(files[i], '.html')] = 'partials/' + files[i];
  };

  // derectly deal with it here
  deal(obj);
});

or you can consider async:

async.waterfall([

    function(cb) {
      fs.readdir(p, cb)
    },
    function(files, cb) {
      for (var i = 0; i < files.length; i++) {
        obj[path.basename(files[i], '.html')] = 'partials/' + files[i];
      }
      cb(null, obj);
    }
  ],
  function(err, obj) {
    if (err) {
      throw err;
    }

    // do somethin else
  }
);

or you want sync return :

var files = fs.readdirSync(p);
for (var i = 0; i < files.length; i++) {
  obj[path.basename(files[i], '.html')] = 'partials/' + files[i];
};

// here's your obj
obj;

read the document for more detail: http://nodejs.org/api/fs.html