Calculated default level when user gave custom levels and doesnt specify level property in logger.

examples/implicit-level.js

@@ -0,0 +1,34 @@
+'use strict';
+
+const winston = require('../');
+const myCustomLevels = {
+    l1: 0,
+    l2:1,
+    l3:2,
+    l4:3,
+    l5:4,
+    l6:5,
+    l7:6,
+    l8:7
+}
+
+/* made customs levels and didn't specify level for cut off-
+but here magic happens and default level is implicitly selected 
+based on custom level using median approach*/
+
+const myNewLogger = winston.createLogger({
+   levels:myCustomLevels,
+      transports: [
+        new winston.transports.Console()
+      ]
+})
+
+myNewLogger.l1("some l1 message");
+myNewLogger.l2("some l2 message");
+myNewLogger.l3("some l3 message");
+myNewLogger.l4("some l4 message");
+myNewLogger.l5("some l5 message");
+myNewLogger.l6("some l6 message");
+
+
+

lib/winston/logger.js

@@ -42,6 +42,10 @@ class Logger extends Transform {
     this.configure(options);
   }
 
+  // method to calculate default level value in case of custom levels defined
+
+
+
   child(defaultRequestMetadata) {
     const logger = this;
     return Object.create(logger, {
@@ -70,6 +74,7 @@ class Logger extends Transform {
     });
   }
 
+
   /**
    * This will wholesale reconfigure this instance by:
    * 1. Resetting all transports. Older transports will be removed implicitly.
@@ -78,12 +83,13 @@ class Logger extends Transform {
    * @param {!Object} options - TODO: add param description.
    * @returns {undefined}
    */
+
   configure({
     silent,
     format,
     defaultMeta,
     levels,
-    level = 'info',
+    level,
     exitOnError = true,
     transports,
     colors,
@@ -95,6 +101,41 @@ class Logger extends Transform {
     exceptionHandlers,
     rejectionHandlers
   } = {}) {
+
+
+    //  function to calculate default levels
+
+   function calculateDefaultLevel({ levels={} }) {
+      // for example : levels:{low:0,medium:1,high:2}
+      // levelNumber=[0,1,2]
+      // levelNames=["low"]
+      const strNumbers = Object.values(levels);
+
+      const levelNumbers = strNumbers.map(function (num) {
+        return Number(num);
+      })
+      const levelNames = Object.keys(levels);
+
+      const sortedLevels = levelNumbers.sort((a, b) => a - b);
+      //now it'll  select median from sorted list as default level value 
+      let medianIndex = Math.floor(sortedLevels.length / 2) - 1;
+      if(medianIndex===-1){
+        // means level have only one key
+        medianIndex=0;
+      }
+      const medianLevelValue = sortedLevels[medianIndex];
+      let defaultLvlName = "info";
+      Object.entries(levels).forEach((level) => {
+        if (parseInt(level[1]) === medianLevelValue) {
+          defaultLvlName = level[0];
+        }
+      })
+
+      return  defaultLvlName;
+
+    }
+
+
     // Reset transports if we already have them
     if (this.transports.length) {
       this.clear();
@@ -106,7 +147,41 @@ class Logger extends Transform {
     this.defaultMeta = defaultMeta || null;
     // Hoist other options onto this instance.
     this.levels = levels || this.levels || config.npm.levels;
-    this.level = level;
+
+
+    // if level is not given and levels are also not given 
+
+    if(Object.keys(levels).length ===1){
+
+    }
+
+
+    if (!level && !levels) {
+      this.level = "info";
+    }
+
+    // user gave custom levels then calculate default value implicitly
+    else if (Object.keys(levels).length > 0 && !level) {
+      this.level = calculateDefaultLevel({
+        levels
+      });
+    }
+
+    // user didnt gave custom levels but gave level
+    else if (!Object.keys(levels).length > 0 && level) {
+      this.level = level;
+    }
+
+    // user didnt gave custom levels but gave level
+    else if (Object.keys(levels).length < 0 && level) {
+      this.level = level;
+    }
+    else if (Object.keys(levels).length > 0 && level){
+      this.level=level
+    }
+
+
+
     if (this.exceptions) {
       this.exceptions.unhandle();
     }