feat: add new method addLevel() to LambdaLog

lib/LambdaLog.js

@@ -93,29 +93,37 @@ class LambdaLog extends EventEmitter {
      */
     this.console = this.options.logHandler;
 
-    this._levels.forEach(lvl => {
-      /**
-       * Shortcut methods for `log.log()`. By default, the following methods are available: `log.info()`, `log.warn()`, `log.error()` and `log.debug()`.
-       * Additional methods will be added for any [custom log levels](#custom-log-levels) provided.<br><br>The provided msg can be any type, although a string
-       * or `Error` is recommended. If `Error` is provided the stack trace is added as metadata to the log as `stack`.
-       * @alias LambdaLog#&lt;info|warn|error|debug|*&gt;
-       * @param {*}      msg  Message to log. Can be any type, but string or `Error` reccommended.
-       * @param {Object} [meta={}] Optional meta data to attach to the log.
-       * @param {Array}  [tags=[]] Additional tags to append to this log.
-       * @return {LogMessage}  The LogMessage instance for the log.
-       *
-       * @example
-       * const log = require('lambda-log');
-       *
-       * log.info('Test info log');
-       * log.debug('Test debug log');
-       * log.warn('Test warn log');
-       * log.error('Test error log');
-       */
-      this[lvl] = (msg, meta = {}, tags = []) => {
-        return this.log(lvl, msg, meta, tags);
-      };
-    });
+    const levelsConfig = this[symbols.LEVELS];
+    for(const lvl in levelsConfig) {
+      if(Object.prototype.hasOwnProperty.call(levelsConfig, lvl)) {
+        this.addLevel(lvl, levelsConfig[lvl]);
+      }
+    }
+  }
+
+  /**
+   * Add a new log level to this instance of LambdaLog.
+   * @since 3.0.0
+   * @param {String} name The name of the new log level.
+   * @param {String|(message: LogMessage) => String} handler The string name of the `console` method to call or a function that returns a string method name.
+   */
+  addLevel(name, handler) {
+    this[symbols.LEVELS][name] = handler;
+
+    /**
+     * Shortcut methods for `log.log()`. By default, the following methods are available: `log.info()`, `log.warn()`, `log.error()` and `log.debug()`.
+     * Additional methods will be added for any [custom log levels](#custom-log-levels) provided.<br><br>The provided msg can be any type, although a string
+     * or `Error` is recommended. If `Error` is provided the stack trace is added as metadata to the log as `stack`.
+     * @param {*}      msg  Message to log. Can be any type, but string or `Error` reccommended.
+     * @param {Object} [meta={}] Optional meta data to attach to the log.
+     * @param {String[]}  [tags=[]] Additional tags to append to this log.
+     * @return {LogMessage}  The LogMessage instance for the log.
+     */
+    this[name] = (msg, meta = {}, tags = []) => {
+      return this.log(name, msg, meta, tags);
+    };
+
+    return this;
   }
 
   /**