Make logger more configurable

index.js

 const { createLogger, format, transports } = require('winston');
 
 
-function adjustLogger (logger, config) {
+function adjustLogger (logger, maxLogLevel) {
   logger.transports.forEach(transport => {
-    transport.level = config.maxLogLevel;
+    transport.level = maxLogLevel;
   });
 }
 
-function initLogger (config) {
+function getFormattedString (info, levels, timestamp) {
+  let result = info.message;
+  if (!levels && !timestamp) {
+    return result;
+  }
+  result = ': ' + result;
+  if (levels) {
+    result = info.level + result;
+  }
+  if (timestamp) {
+    result = info.timestamp + ' ' + result;
+  }
+  return result;
+}
+
+function initLogger ({
+  colors = true,
+  file = null,
+  levels = true,
+  maxLogLevel = 'info',
+  timestamp = true
+}) {
+  const transforms = [
+    format(info => {
+      info.timestamp = new Date().toLocaleString();
+      return info;
+    })(),
+    ...(colors ? [format.colorize()] : []),
+    format.printf(info => getFormattedString(info, levels, timestamp))
+  ];
+
+  const transport = (typeof file === 'string') ? new transports.File({
+    filename: file
+  }) : new transports.Console();
+
   const logger = createLogger({
-    format: format.combine(
-      format(info => {
-        info.timestamp = new Date().toLocaleString();
-        return info;
-      })(),
-      format.colorize(),
-      format.printf(info => `${info.timestamp} ${info.level}: ${info.message}`)
-    ),
+    format: format.combine(...transforms),
     transports: [
-      new transports.Console()
+      transport
     ]
   });
-  adjustLogger(logger, config);
+
+  adjustLogger(logger, maxLogLevel);
   return logger;
 }