Npm Utilities

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In this project we are going to start creating some utilities and put them in our NPM package. We will then create a project and use our utilities.

Step One

Put the following utilities in you npm package in a file called utils.js:

Maybe utils.js should look something like this, as a starting point:

module.exports = {
    writeFile: function(fileName, contents, callback) {
        callback({ "result": "writeFile Result TBD"});
    readFile: function(fileName, callback) {
        callback({ "result": "readFile Result TBD"});
    padNumber: function(numberToPad, width, padValue) {
        return { "result": "numberToPad result TBD"};

And then we need to ask our npm module index.js file to pass this along to the rest of the world:

var utils = require('./utils');

exports.getPackageDescription = function() {
  var myDescription = "This is Charlie Calvert's isit322 test package";
  return myDescription;

exports.getNine = function() { return 9; };

exports.utils = utils;

Do you see what is going on here? We requre our utils module at the top of the file. Then we export it at the bottom.

Update the version of your package and then push it to NPM:

npm version minor
npm publish

Step Two

Create a project

CreateAllExpress Week03-UseNpmPackage

Install your package. For instance, I type:

npm install isit322-calvert --save

Commands you can use to learn more about a package:

npm show

For instance:

  npm show isit322-kariungi
  npm show isit322-calvert

Typical output:

{ name: 'isit322-calvert',
  description: 'My test package',
  'dist-tags': { latest: '1.1.3' },
  versions: [ '1.0.0', '1.0.1', '1.0.2', '1.1.0', '1.1.1', '1.1.2', '1.1.3' ],
  maintainers: [ 'charliecalvert ' ],
   { modified: '2016-02-04T03:12:54.452Z',
     created: '2016-01-14T02:09:55.073Z',
     '1.0.0': '2016-01-14T02:09:55.073Z',
     '1.0.1': '2016-01-14T02:19:59.955Z',
     '1.0.2': '2016-01-14T02:59:12.265Z',
     '1.1.0': '2016-01-20T01:53:08.120Z',
     '1.1.1': '2016-01-20T02:10:53.173Z',
     '1.1.2': '2016-01-20T02:18:01.199Z',
     '1.1.3': '2016-02-04T03:12:54.452Z' },
  keywords: [ 'npm', 'test' ],
   { type: 'git',
     url: 'git@bitbucket:ccalvert/isit322-calvert-2016.git' },
  author: 'Charlie Calvert',
  license: 'MIT',
  readmeFilename: '',
  version: '1.1.3',
  main: 'index.js',
  scripts: { test: 'echo "Error: no test specified" && exit 1' },
   { shasum: '8a17e79386028001a3f84cd304be1e266ef57085',
     tarball: '' },
  directories: {} }


npm show isit322-kariungi version

Step Three

Now we want to be able to call each of these functions from our npm utils module. On the server side, here is how to use one function as I defined it above:

var utils = require('isit322-calvert').utils;

Or, if you are willing to trade a bit of typing for some additional flexibility, like this:

var isit = require('isit322-calvert');
var utils = isit.utils;

NOTE: You should, of course, be loading your NPM package, not mine. Where I write calvert, you should be writing your last name.

Now use one of the methods from your package:

router.get('/readFile', function(request, response) {
    utils.readFile('sam.txt', function(result) {

Step Four

On the client side, something like this:

$(document).ready(function() { 'use strict';
    $.getJSON('/readFile', function(result) {
    }).done(function() {
     showDebug( "readFile second success" );
    .fail(function(jqxhr, textStatus, error) {
        showDebug( "readFile error: " + jqxhr.status + ' ' + textStatus + ' ' + error );
    .always(function() {
        showDebug( "readFile complete" );

Back on the server side, add this to index.jade:


Step Five

You should call all the functions in your npm library. I suppose that should both the two in index.js and the ones in utils.js. Show the results from each call in a separate PRE tag.

You should fully implement all the methods in the npm package. You will need, of course, to use fs.readFile and fs.writeFile.

And you will need to require fs:

var fs = require('fs');

You will also have to pass the name of files to read and write to the server. For now, you can hardcode the values you pass from the client to the server, like this:

var fileToRead = { fileName: 'qux.txt' };
$.getJSON('/readFile', fileToRead,  function(result) {

I also want you to pass in the arguments that padNumber receives. In other words, when you call getJSON, I want you to pass values such as 5, 3 and '0' to the server side. On the server, you should use the request.query object to get the values passed from the client to the server. As shown above, When calling getJSON, use the second parameter to create an object that specifies the values you want to pass. A brief related discussion is found here:

Of course, if you want to build a real front with buttons and input controls, you can, but that is not a requirement at this time. But you should read and write real files on the server side.

Turn it in

Push your work from your local drive to your repository and submit the assignment. Best to mention github url when submitting assignment.

Pad Number

Given the number 5, the following call sets result to the string '005':

var result = padNumber(5, 3, '0');

But of course, in our code, padNumber would be a method of the utils object:

var result = utils.padNumber(5, 3, '0');


I found that I would install my package, only to find it did not work right. At that point, I could: