make options objects private and fix label config

Author: digitalsadhu

lib/counter.js

@@ -13,10 +13,12 @@ const Counter = class Counter extends EventEmitter {
             `argument 'options' must be provided`,
         );
 
-        this.options = {
-            labels: {},
-            ...options,
-        };
+        Object.defineProperty(this, 'options', {
+            value: {
+                labels: {},
+                ...options,
+            },
+        });
     }
 
     inc(value, options) {

lib/gauge.js

@@ -13,10 +13,12 @@ const Gauge = class Gauge extends EventEmitter {
             `argument 'options' must be provided`,
         );
 
-        this.options = {
-            labels: [],
-            ...options,
-        };
+        Object.defineProperty(this, 'options', {
+            value: {
+                labels: {},
+                ...options,
+            },
+        });
     }
 
     set(value, options = {}) {

lib/histogram.js

@@ -16,10 +16,12 @@ const Histogram = class Histogram extends EventEmitter {
 
         // TODO: validate optional buckets option
 
-        this.options = {
-            labels: [],
-            ...options,
-        };
+        Object.defineProperty(this, 'options', {
+            value: {
+                labels: {},
+                ...options,
+            },
+        });
     }
 
     observe(value, options = {}) {

lib/summary.js

@@ -16,10 +16,12 @@ const Summary = class Summary extends EventEmitter {
 
         // TODO: validate optional quantiles option
 
-        this.options = {
-            labels: [],
-            ...options,
-        };
+        Object.defineProperty(this, 'options', {
+            value: {
+                labels: {},
+                ...options,
+            },
+        });
     }
 
     observe(value, options = {}) {