Extract getUsbEndpoints() to util.js. Use ES6 features in led_pwm.js

usb/led_pwm.js

@@ -1,39 +1,19 @@
 #!/usr/bin/env node
-'use strict';
+let util = require('./util');
 
-var usb = require('usb');
-var util = require('./util');
+let LED_PWM_COMMAND_ID = 10;
+let [endpointIn, endpointOut] = util.getUsbEndpoints();
+let brightnessPercent = 0;
 
-var vid = 0x16d3;
-var pid = 0x05ea;
-var LED_PWM_COMMAND_ID = 10;
-
-var device = usb.findByIds(vid, pid);
-device.open();
-
-var usbInterface = device.interface(0);
-
-// https://github.com/tessel/node-usb/issues/147
-// The function 'isKernelDriverActive' is not available on Windows and not even needed.
-if (process.platform !== 'win32' && usbInterface.isKernelDriverActive()) {
-    usbInterface.detachKernelDriver();
-}
-usbInterface.claim();
-
-var endpointIn = usbInterface.endpoints[0];
-var endpointOut = usbInterface.endpoints[1];
-
-var brightnessPercent = 0;
-
-setInterval(function() {
+setInterval(() => {
     brightnessPercent = brightnessPercent ? 0 : 100
     console.log('Sending ', brightnessPercent);
-    endpointOut.transfer(new Buffer([LED_PWM_COMMAND_ID, brightnessPercent]), function(err) {
+    endpointOut.transfer(new Buffer([LED_PWM_COMMAND_ID, brightnessPercent]), err => {
         if (err) {
             console.error("USB error: %s", err);
             process.exit(1);
         }
-        endpointIn.transfer(64, function(err2, receivedBuffer) {
+        endpointIn.transfer(64, (err2, receivedBuffer) => {
             if (err2) {
                 console.error("USB error: %s", err2);
                 process.exit(2);
@@ -41,4 +21,4 @@ setInterval(function() {
             console.log('Received', util.bufferToString(receivedBuffer));
         })
     });
-}, 500)
+}, 500);

usb/util.js

@@ -1,4 +1,27 @@
+var usb = require('usb');
+
 exports = module.exports = {
+    getUsbEndpoints: function() {
+        var vid = 0x16d3;
+        var pid = 0x05ea;
+
+        var device = usb.findByIds(vid, pid);
+        device.open();
+
+        var usbInterface = device.interface(0);
+
+        // https://github.com/tessel/node-usb/issues/147
+        // The function 'isKernelDriverActive' is not available on Windows and not even needed.
+        if (process.platform !== 'win32' && usbInterface.isKernelDriverActive()) {
+            usbInterface.detachKernelDriver();
+        }
+        usbInterface.claim();
+
+        var endpointIn = usbInterface.endpoints[0];
+        var endpointOut = usbInterface.endpoints[1];
+        return [endpointIn, endpointOut];
+    },
+
     bufferToString: function(buffer) {
         var str = '';
         for (var i = 0; i < buffer.length; i++) {