Training Guide: Programming in HTML5 with JavaScript and CSS3 Ebook

346 CHAPTER 8 Websites and services

The following is a typical folder structure for creating a package. You start by creating a

root folder for your package.

\packageName

\bin

main.js

\lib

module1.js

module2.js

package.json

README.md

Inside the package root folder, you have a package.json file, which is the manifest file. You

also need a README.md file containing enough help to get the user started. In addition, you

need a bin folder and a lib folder. The bin folder contains the entry point to your package; the

lib folder contains the modules.

In this example, the package root folder is created at C:\node_samples\math_example;

math_example is the package name.

In the lib folder, the first module is created, called call_counter.js, which has the following

code.

var internal_call_counter=0;

function count_call(){

++internal_call_counter;

console.log('You have made ' + internal_call_counter + ' calls!');

}

module.exports = count_call;

It looks like the internal_call_counter variable and the count_call function are polluting the

global namespace, but this module code will be wrapped so that neither will be in the global

namespace. You can define what is available when a user uses the require(‘call_counter’)

function by assigning something to module.exports. In this case, the only exported function is

count_call, but you can specify multiple functions by wrapping them in an object, as you’ll see

in the simple_math.js and advanced_math.js modules.

The next module created in the lib folder is simple_math.js, which has the following code.

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

function add(x, y){

call_counter();

return x + y;

}

function subtract(x, y){

call_counter();

return x - y;

}