diff --git a/lib/utils.js b/lib/utils.js
index 483287269..a39befd5b 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -5,193 +5,265 @@ let Semver = require('semver');
 let URL = require('url');
 let Logger = require('./logger');
 
-module.exports.validate_package = function(name) {
-  name = name.split('/', 2);
-  if (name.length === 1) {
-    // normal package
-    return module.exports.validate_name(name[0]);
-  } else {
-    // scoped package
-    return name[0][0] === '@'
-        && module.exports.validate_name(name[0].slice(1))
-        && module.exports.validate_name(name[1]);
-  }
-};
+/**
+ * Validate a package.
+ * @param {*} name
+ * @return {Boolean} whether the package is valid or not
+ */
+function validate_package(name) {
+	name = name.split('/', 2);
+	if (name.length === 1) {
+		// normal package
+		return module.exports.validate_name(name[0]);
+	} else {
+		// scoped package
+		return name[0][0] === '@'
+				&& module.exports.validate_name(name[0].slice(1))
+				&& module.exports.validate_name(name[1]);
+	}
+}
 
-// from normalize-package-data/lib/fixer.js
-module.exports.validate_name = function(name) {
-  if (typeof(name) !== 'string') return false;
-  name = name.toLowerCase();
+/**
+ * From normalize-package-data/lib/fixer.js
+ * @param {*} name  the package name
+ * @return {Boolean} whether is valid or not
+ */
+function validate_name(name) {
+	if (typeof(name) !== 'string') {
+		return false;
+	}
+	name = name.toLowerCase();
 
-  // all URL-safe characters and "@" for issue #75
-  if (!name.match(/^[-a-zA-Z0-9_.!~*'()@]+$/)
-   || name.charAt(0) === '.' // ".bin", etc.
-   || name.charAt(0) === '-' // "-" is reserved by couchdb
-   || name === 'node_modules'
-   || name === '__proto__'
-   || name === 'package.json'
-   || name === 'favicon.ico'
-  ) {
-    return false;
-  } else {
-    return true;
-  }
-};
+	// all URL-safe characters and "@" for issue #75
+	if (!name.match(/^[-a-zA-Z0-9_.!~*'()@]+$/)
+	 || name.charAt(0) === '.' // ".bin", etc.
+	 || name.charAt(0) === '-' // "-" is reserved by couchdb
+	 || name === 'node_modules'
+	 || name === '__proto__'
+	 || name === 'package.json'
+	 || name === 'favicon.ico'
+	) {
+		return false;
+	} else {
+		return true;
+	}
+}
 
-module.exports.is_object = function(obj) {
-  return typeof(obj) === 'object' && obj !== null && !Array.isArray(obj);
-};
+/**
+ * Check whether an element is an Object
+ * @param {*} obj the element
+ * @return {Boolean}
+ */
+function is_object(obj) {
+	return typeof(obj) === 'object' && obj !== null && !Array.isArray(obj);
+}
 
-module.exports.validate_metadata = function(object, name) {
-  assert(module.exports.is_object(object), 'not a json object');
-  assert.equal(object.name, name);
+/**
+ * Validate the package metadata, add additional properties whether are missing within
+ * the metadata properties.
+ * @param {*} object
+ * @param {*} name
+ * @return {Object} the object with additional properties as dist-tags ad versions
+ */
+function validate_metadata(object, name) {
+	assert(module.exports.is_object(object), 'not a json object');
+	assert.equal(object.name, name);
 
-  if (!module.exports.is_object(object['dist-tags'])) {
-    object['dist-tags'] = {};
-  }
+	if (!module.exports.is_object(object['dist-tags'])) {
+		object['dist-tags'] = {};
+	}
 
-  if (!module.exports.is_object(object['versions'])) {
-    object['versions'] = {};
-  }
+	if (!module.exports.is_object(object['versions'])) {
+		object['versions'] = {};
+	}
 
-  return object;
-};
+	return object;
+}
 
-module.exports.filter_tarball_urls = function(pkg, req, config) {
-  function filter(_url) {
-    if (!req.headers.host) return _url;
+/**
+ * Iterate a packages's versions and filter each original tarbal url.
+ * @param {*} pkg
+ * @param {*} req
+ * @param {*} config
+ * @return {String} a filtered package
+ */
+function filter_tarball_urls(pkg, req, config) {
+	/**
+	 * Filter a tarball url.
+	 * @param {*} _url
+	 * @return {String} a parsed url
+	 */
+	const filter = function(_url) {
+		if (!req.headers.host) {
+			return _url;
+		}
+		let filename = URL.parse(_url).pathname.replace(/^.*\//, '');
+		let result;
+		if (config.url_prefix != null) {
+			result = config.url_prefix.replace(/\/$/, '');
+		} else {
+			result = req.protocol + '://' + req.headers.host;
+		}
+		return `${result}/${pkg.name.replace(/\//g, '%2f')}/-/${filename}`;
+	};
 
-    let filename = URL.parse(_url).pathname.replace(/^.*\//, '');
+	for (let ver in pkg.versions) {
+		let dist = pkg.versions[ver].dist;
+		if (dist != null && dist.tarball != null) {
+			// dist.__verdaccio_orig_tarball = dist.tarball
+			dist.tarball = filter(dist.tarball);
+		}
+	}
+	return pkg;
+}
 
-    if (config.url_prefix != null) {
-      var result = config.url_prefix.replace(/\/$/, '');
-    } else {
-      var result = req.protocol + '://' + req.headers.host;
-    }
+/**
+ * Create a tag for a package
+ * @param {*} data
+ * @param {*} version
+ * @param {*} tag
+ * @return {Boolean} whether a package has been tagged
+ */
+function tag_version(data, version, tag) {
+	if (tag) {
+		if (data['dist-tags'][tag] !== version) {
+			if (Semver.parse(version, true)) {
+				// valid version - store
+				data['dist-tags'][tag] = version;
+				return true;
+			}
+		}
+		Logger.logger.warn({ver: version, tag: tag}, 'ignoring bad version @{ver} in @{tag}');
+		if (tag && data['dist-tags'][tag]) {
+			delete data['dist-tags'][tag];
+		}
+	}
+	return false;
+}
 
-    return `${result}/${pkg.name.replace(/\//g, '%2f')}/-/${filename}`;
-  }
+/**
+ * Gets version from a package object taking into account semver weirdness.
+ * @param {*} object
+ * @param {*} version
+ * @return {String} return the semantic version of a package
+ */
+function get_version(object, version) {
+	// this condition must allow cast
+	if (object.versions[version] != null) {
+		return object.versions[version];
+	}
+	try {
+		version = Semver.parse(version, true);
+		for (let k in object.versions) {
+			if (version.compare(Semver.parse(k, true)) === 0) {
+				return object.versions[k];
+			}
+		}
+	} catch (err) {
+		return undefined;
+	}
+}
 
-  for (let ver in pkg.versions) {
-    let dist = pkg.versions[ver].dist;
-    if (dist != null && dist.tarball != null) {
-      // dist.__verdaccio_orig_tarball = dist.tarball
-      dist.tarball = filter(dist.tarball);
-    }
-  }
-  return pkg;
-};
+/**
+ * Parse an internet address
+ * Allow:
+		- https:localhost:1234        - protocol + host + port
+		- localhost:1234              - host + port
+		- 1234                        - port
+		- http::1234                  - protocol + port
+		- https://localhost:443/      - full url + https
+		- http://[::1]:443/           - ipv6
+		- unix:/tmp/http.sock         - unix sockets
+		- https://unix:/tmp/http.sock - unix sockets (https)
+ * @param {*} addr the internet address definition
+ * @return {Object|Null} literal object that represent the address parsed
+ */
+function parse_address(addr) {
+	//
+	// TODO: refactor it to something more reasonable?
+	//
+	//        protocol :  //      (  host  )|(    ipv6     ):  port  /
+	let m = /^((https?):(\/\/)?)?((([^\/:]*)|\[([^\[\]]+)\]):)?(\d+)\/?$/.exec(addr);
 
-module.exports.tag_version = function(data, version, tag) {
-  if (tag) {
-    if (data['dist-tags'][tag] !== version) {
-      if (Semver.parse(version, true)) {
-        // valid version - store
-        data['dist-tags'][tag] = version;
-        return true;
-      }
-    }
-    Logger.logger.warn({ver: version, tag: tag}, 'ignoring bad version @{ver} in @{tag}');
-    if (tag && data['dist-tags'][tag]) {
-      delete data['dist-tags'][tag];
-    }
-  }
-  return false;
-};
+	if (m) return {
+		proto: m[2] || 'http',
+		host: m[6] || m[7] || 'localhost',
+		port: m[8] || '4873',
+	};
 
-// gets version from a package object taking into account semver weirdness
-module.exports.get_version = function(object, version) {
-  if (object.versions[version] != null) return object.versions[version];
+	m = /^((https?):(\/\/)?)?unix:(.*)$/.exec(addr);
 
-  try {
-    version = Semver.parse(version, true);
-    for (let k in object.versions) {
-      if (version.compare(Semver.parse(k, true)) === 0) {
-        return object.versions[k];
-      }
-    }
-  } catch (err) {
-    return undefined;
-  }
-};
+	if (m) {
+		return {
+			proto: m[2] || 'http',
+			path: m[4],
+		};
+	}
 
-module.exports.parse_address = function parse_address(addr) {
-  //
-  // Allow:
-  //
-  //  - https:localhost:1234        - protocol + host + port
-  //  - localhost:1234              - host + port
-  //  - 1234                        - port
-  //  - http::1234                  - protocol + port
-  //  - https://localhost:443/      - full url + https
-  //  - http://[::1]:443/           - ipv6
-  //  - unix:/tmp/http.sock         - unix sockets
-  //  - https://unix:/tmp/http.sock - unix sockets (https)
-  //
-  // TODO: refactor it to something more reasonable?
-  //
-  //        protocol :  //      (  host  )|(    ipv6     ):  port  /
-  var m = /^((https?):(\/\/)?)?((([^\/:]*)|\[([^\[\]]+)\]):)?(\d+)\/?$/.exec(addr);
+	return null;
+}
 
-  if (m) return {
-    proto: m[2] || 'http',
-    host: m[6] || m[7] || 'localhost',
-    port: m[8] || '4873',
-  };
+/**
+ * Function filters out bad semver versions and sorts the array.
+ * @param {*} array
+ * @return {Array} sorted Array
+ */
+function semver_sort(array) {
+	return array
+		.filter(function(x) {
+			if (!Semver.parse(x, true)) {
+				Logger.logger.warn( {ver: x}, 'ignoring bad version @{ver}' );
+				return false;
+			}
+			return true;
+		})
+		.sort(Semver.compareLoose)
+		.map(String);
+}
 
-  var m = /^((https?):(\/\/)?)?unix:(.*)$/.exec(addr);
+/**
+ * Flatten arrays of tags.
+ * @param {*} data
+ */
+function normalize_dist_tags(data) {
+	let sorted;
 
-  if (m) return {
-    proto: m[2] || 'http',
-    path: m[4],
-  };
+	if (!data['dist-tags'].latest) {
+		// overwrite latest with highest known version based on semver sort
+		sorted = module.exports.semver_sort(Object.keys(data.versions));
+		if (sorted && sorted.length) {
+				data['dist-tags'].latest = sorted.pop();
+		}
+	}
 
-  return null;
-};
+	for (let tag in data['dist-tags']) {
+		if (Array.isArray(data['dist-tags'][tag])) {
+			if (data['dist-tags'][tag].length) {
+				// sort array
+				sorted = module.exports.semver_sort(data['dist-tags'][tag]);
+				if (sorted.length) {
+						// use highest version based on semver sort
+						data['dist-tags'][tag] = sorted.pop();
+				}
+			} else {
+				delete data['dist-tags'][tag];
+			}
+		} else if (typeof data['dist-tags'][tag] === 'string') {
+			if (!Semver.parse(data['dist-tags'][tag], true)) {
+				// if the version is invalid, delete the dist-tag entry
+				delete data['dist-tags'][tag];
+			}
+		}
+	}
+}
 
-// function filters out bad semver versions and sorts the array
-module.exports.semver_sort = function semver_sort(array) {
-  return array
-        .filter(function(x) {
-          if (!Semver.parse(x, true)) {
-            Logger.logger.warn( {ver: x}, 'ignoring bad version @{ver}' );
-            return false;
-          }
-          return true;
-        })
-        .sort(Semver.compareLoose)
-        .map(String);
-};
-
-// flatten arrays of tags
-module.exports.normalize_dist_tags = function(data) {
-  let sorted;
-
-  if (!data['dist-tags'].latest) {
-    // overwrite latest with highest known version based on semver sort
-    sorted = module.exports.semver_sort(Object.keys(data.versions));
-    if (sorted && sorted.length) {
-        data['dist-tags'].latest = sorted.pop();
-    }
-  }
-
-  for (let tag in data['dist-tags']) {
-    if (Array.isArray(data['dist-tags'][tag])) {
-      if (data['dist-tags'][tag].length) {
-        // sort array
-        sorted = module.exports.semver_sort(data['dist-tags'][tag]);
-        if (sorted.length) {
-            // use highest version based on semver sort
-            data['dist-tags'][tag] = sorted.pop();
-        }
-      } else {
-        delete data['dist-tags'][tag];
-      }
-    } else if (typeof data['dist-tags'][tag] === 'string') {
-      if (!Semver.parse(data['dist-tags'][tag], true)) {
-        // if the version is invalid, delete the dist-tag entry
-        delete data['dist-tags'][tag];
-      }
-    }
-  }
-};
+module.exports.semver_sort = semver_sort;
+module.exports.parse_address = parse_address;
+module.exports.get_version = get_version;
+module.exports.normalize_dist_tags = normalize_dist_tags;
+module.exports.tag_version = tag_version;
+module.exports.filter_tarball_urls = filter_tarball_urls;
+module.exports.validate_metadata = validate_metadata;
+module.exports.is_object = is_object;
+module.exports.validate_name = validate_name;
+module.exports.validate_package = validate_package;