Weird or i'm doing something wrong ?

shell.log

➜  logcatIO git:(master) ✗ npm run build

> logcatio@0.0.3 build /Users/vruno/Documents/Urucas/Node/logcatIO
> babel lib/ --out-dir dist/

lib/index.js -> dist/index.js
➜  logcatIO git:(master) ✗ cat dist/index.js

import socketio from 'socket.io';
import semafor from 'semafor';
import os from 'os';
import http from 'http';
import express from 'express';
import path from 'path';

export default function server(port) {
  let logger = semafor();
  let app = express();
  let server = http.Server(app);
  let io = socketio(server);

  let public_path = path.join(__dirname, '..', 'public');
  app.use(express.static(public_path));

  let ifaces = os.networkInterfaces();
  let en1 = ifaces["en1"];
  let local_ip;
  for (let i in en1) {
    var addr = en1[i];
    if (addr.family != "IPv4") continue;
    local_ip = ["http", addr.address].join("://");
    break;
  }
  let namespace = [local_ip, port].join(":");

  io.on("connection", socket => {
    console.log("connection");
    let _card = {};
    socket.on("greetings", card => {
      console.log("greetings");
      _card = card;
      io.emit("greetings", card);
    });
    socket.on("dump", log => {
      console.log("dump");
      io.emit("dump", log);
    });
    socket.on("disconnect", () => {
      console.log("disconnect");
      io.emit("goodbye", _card);
    });
  });

  server.listen(port, () => {
    logger.ok(`Server running on ${ namespace }`);
  });
}%    

➜  logcatIO git:(master) ✗ rm dist/index.js
➜  logcatIO git:(master) ✗ babel lib/ --out-dir dist/
lib/index.js -> dist/index.js
➜  logcatIO git:(master) ✗ cat dist/index.js

"use strict";

var _interopRequire = function (obj) { return obj && obj.__esModule ? obj["default"] : obj; };

module.exports = server;

var socketio = _interopRequire(require("socket.io"));

var semafor = _interopRequire(require("semafor"));

var os = _interopRequire(require("os"));

var http = _interopRequire(require("http"));

var express = _interopRequire(require("express"));

var path = _interopRequire(require("path"));

function server(port) {
  var logger = semafor();
  var app = express();
  var server = http.Server(app);
  var io = socketio(server);

  var public_path = path.join(__dirname, "..", "public");
  app.use(express["static"](public_path));

  var ifaces = os.networkInterfaces();
  var en1 = ifaces.en1;
  var local_ip = undefined;
  for (var i in en1) {
    var addr = en1[i];
    if (addr.family != "IPv4") continue;
    local_ip = ["http", addr.address].join("://");
    break;
  }
  var namespace = [local_ip, port].join(":");

  io.on("connection", function (socket) {
    console.log("connection");
    var _card = {};
    socket.on("greetings", function (card) {
      console.log("greetings");
      _card = card;
      io.emit("greetings", card);
    });
    socket.on("dump", function (log) {
      console.log("dump");
      io.emit("dump", log);
    });
    socket.on("disconnect", function () {
      console.log("disconnect");
      io.emit("goodbye", _card);
    });
  });

  server.listen(port, function () {
    logger.ok("Server running on " + namespace);
  });
}%                                                                                       
➜  logcatIO git:(master) ✗

Can't tell what babel version you are using - if you are using babel 6 it won't do anything by default so you should make a .babelrc file. https://github.com/thejameskyle/babel-handbook/blob/master/translations/en/user-handbook.md#configuring-babel

Yeah, my mistake. I'm using "babel-cli": "^6.4.5". I'll check the user-handbock.

Fixed change my build script from:
babel lib/ --out-dir dist/
to
babel dist -d lib

Nope sorry, I tried in the shell and it worked but still not working under npm run build

Fixed,
npm install --save-dev babel-preset-es2015
and create a .babelrc file

{
  "presets": ["es2015"],
  "plugins": []
}