Merge pull request #970 from vmarchesin/fix-memory-leak-issue-952

[FIX] Resolve #952 - memory leak in createEventHub

snippet_data/snippets.json

@@ -965,8 +965,8 @@
         "fileName": "createEventHub.md",
         "text": "Creates a pub/sub ([publish–subscribe](https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern)) event hub with `emit`, `on`, and `off` methods.\n\nUse `Object.create(null)` to create an empty `hub` object that does not inherit properties from `Object.prototype`.\nFor `emit`, resolve the array of handlers based on the `event` argument and then run each one with `Array.prototype.forEach()` by passing in the data as an argument.\nFor `on`, create an array for the event if it does not yet exist, then use `Array.prototype.push()` to add the handler\nto the array.\nFor `off`, use `Array.prototype.findIndex()` to find the index of the handler in the event array and remove it using `Array.prototype.splice()`.",
         "codeBlocks": {
-          "es6": "const createEventHub = () => ({\n  hub: Object.create(null),\n  emit(event, data) {\n    (this.hub[event] || []).forEach(handler => handler(data));\n  },\n  on(event, handler) {\n    if (!this.hub[event]) this.hub[event] = [];\n    this.hub[event].push(handler);\n  },\n  off(event, handler) {\n    const i = (this.hub[event] || []).findIndex(h => h === handler);\n    if (i > -1) this.hub[event].splice(i, 1);\n  }\n});",
+          "es6": "const createEventHub = () => ({\n  hub: Object.create(null),\n  emit(event, data) {\n    (this.hub[event] || []).forEach(handler => handler(data));\n  },\n  on(event, handler) {\n    if (!this.hub[event]) this.hub[event] = [];\n    this.hub[event].push(handler);\n  },\n  off(event, handler) {\n    const i = (this.hub[event] || []).findIndex(h => h === handler);\n    if (i > -1) this.hub[event].splice(i, 1);\n    if (this.hub[event].length === 0) delete this.hub[event]\n  }\n});",
-          "es5": "var createEventHub = function createEventHub() {\n  return {\n    hub: Object.create(null),\n    emit: function emit(event, data) {\n      (this.hub[event] || []).forEach(function (handler) {\n        return handler(data);\n      });\n    },\n    on: function on(event, handler) {\n      if (!this.hub[event]) this.hub[event] = [];\n      this.hub[event].push(handler);\n    },\n    off: function off(event, handler) {\n      var i = (this.hub[event] || []).findIndex(function (h) {\n        return h === handler;\n      });\n      if (i > -1) this.hub[event].splice(i, 1);\n    }\n  };\n};",
+          "es5": "var createEventHub = function createEventHub() {\n  return {\n    hub: Object.create(null),\n    emit: function emit(event, data) {\n      (this.hub[event] || []).forEach(function (handler) {\n        return handler(data);\n      });\n    },\n    on: function on(event, handler) {\n      if (!this.hub[event]) this.hub[event] = [];\n      this.hub[event].push(handler);\n    },\n    off: function off(event, handler) {\n      var i = (this.hub[event] || []).findIndex(function (h) {\n        return h === handler;\n      });\n      if (i > -1) this.hub[event].splice(i, 1);\n      if (this.hub[event].length === 0) delete this.hub[event]\n    }\n  };\n};",
           "example": "const handler = data => console.log(data);\nconst hub = createEventHub();\nlet increment = 0;\n\n// Subscribe: listen for different types of events\nhub.on('message', handler);\nhub.on('message', () => console.log('Message event fired'));\nhub.on('increment', () => increment++);\n\n// Publish: emit events to invoke all handlers subscribed to them, passing the data to them as an argument\nhub.emit('message', 'hello world'); // logs 'hello world' and 'Message event fired'\nhub.emit('message', { hello: 'world' }); // logs the object and 'Message event fired'\nhub.emit('increment'); // `increment` variable is now 1\n\n// Unsubscribe: stop a specific handler from listening to the 'message' event\nhub.off('message', handler);"
         },
         "tags": [

snippets/createEventHub.md

@@ -21,6 +21,7 @@ const createEventHub = () => ({
   off(event, handler) {
     const i = (this.hub[event] || []).findIndex(h => h === handler);
     if (i > -1) this.hub[event].splice(i, 1);
+    if (this.hub[event].length === 0) delete this.hub[event];
   }
 });
 ```

vscode_snippets/snippets.json

@@ -423,6 +423,7 @@
       "  off(event, handler) {",
       "    const i = (this.hub[event] || []).findIndex(h => h === handler);",
       "    if (i > -1) this.hub[event].splice(i, 1);",
+      "    if (this.hub[event].length === 0) delete this.hub[event];",
       "  }",
       "});"
     ],