fix memory leak within debug instance

Author: Qix-

src/common.js

@@ -17,11 +17,6 @@ function setup(env) {
 createDebug[key] = env[key];
 });
 
-/**
-* Active `debug` instances.
-*/
-createDebug.instances = [];
-
 /**
 * The currently active debug mode names, and names to skip.
 */
@@ -63,6 +58,7 @@ function setup(env) {
 */
 function createDebug(namespace) {
 let prevTime;
+let enableOverride = null;
 
 function debug(...args) {
 // Disabled?
@@ -115,31 +111,27 @@ function setup(env) {
 }
 
 debug.namespace = namespace;
-debug.enabled = createDebug.enabled(namespace);
 debug.useColors = createDebug.useColors();
 debug.color = createDebug.selectColor(namespace);
-debug.destroy = destroy;
 debug.extend = extend;
 
+Object.defineProperty(debug, 'enabled', {
+enumerable: true,
+configurable: false,
+get: () => enableOverride === null ? createDebug.enabled(namespace) : enableOverride,
+set: v => {
+enableOverride = v;
+}
+});
+
 // Env-specific initialization logic for debug instances
 if (typeof createDebug.init === 'function') {
 createDebug.init(debug);
 }
 
-createDebug.instances.push(debug);
-
 return debug;
 }
 
-function destroy() {
-const index = createDebug.instances.indexOf(this);
-if (index !== -1) {
-createDebug.instances.splice(index, 1);
-return true;
-}
-return false;
-}
-
 function extend(namespace, delimiter) {
 const newDebug = createDebug(this.namespace + (typeof delimiter === 'undefined' ? ':' : delimiter) + namespace);
 newDebug.log = this.log;
@@ -177,11 +169,6 @@ function setup(env) {
 createDebug.names.push(new RegExp('^' + namespaces + '$'));
 }
 }
-
-for (i = 0; i < createDebug.instances.length; i++) {
-const instance = createDebug.instances[i];
-instance.enabled = createDebug.enabled(instance.namespace);
-}
 }
 
 /**