Optimizations (Parcel + CompositeDisposable + Disposable + Emitter)

.gitignore

@@ -6,3 +6,4 @@ npm-debug.log
 api.json
 dist
 package-lock.json
+.parcel-cache

.npmignore

@@ -6,3 +6,4 @@ src
 npm-debug.log
 .travis.yml
 .pairs
+.parcel-cache

README.md

@@ -75,8 +75,15 @@ const {Disposable} = require('event-kit')
 const disposable = new Disposable(() => this.destroyResource())
 ```
 
-### Using ES6 Code
-You can use the ES6 style classes from `lib` directory.
+### ES6 Classes
+For backward compatibility, the main entry of this package uses prototypical functions instead of classes. To use the version of the code that use classes, there are two options:
+
+- The bundled code:
+```
+const {Disposable, Emitter, CompositeDisposable} = require('event-kit/dist/event-kit.bundle')
+```
+
+- The source code:
 ```
-const {Disposable} = require('event-kit/lib/event-kit')
+const {Disposable, Emitter, CompositeDisposable} = require('event-kit/lib/event-kit')
 ```

appveyor.yml

@@ -1,3 +1,5 @@
+image: Visual Studio 2017
+
 environment:
   matrix:
     - nodejs_version: "10"

babel.config.js

@@ -1,6 +1,8 @@
 let presets = ["babel-preset-atomic"];
 
-let plugins = ["@babel/plugin-transform-classes"] // this is needed so Disposabale can be extended by ES5-style classes
+let plugins = process.env.PARCEL_ENV
+  ? [] // the optimized bundle uses ES6 class
+  : ["@babel/plugin-transform-classes"] // this is needed so Disposabale can be extended by ES5-style classes
 
 module.exports = {
   presets: presets,

lib/composite-disposable.js

@@ -1,5 +1,4 @@
-let CompositeDisposable
-let Disposable
+import Disposable from "./disposable"
 
 // Essential: An object that aggregates multiple {Disposable} instances together
 // into a single disposable, so they can all be disposed as a group.
@@ -24,18 +23,15 @@ let Disposable
 //   }
 // }
 // ```
-module.exports = class CompositeDisposable {
+export default class CompositeDisposable {
   /*
   Section: Construction and Destruction
   */
 
   // Public: Construct an instance, optionally with one or more disposables
-  constructor() {
+  constructor(...args) {
     this.disposed = false
-    this.disposables = new Set()
-    for (let disposable of arguments) {
-      this.add(disposable)
-    }
+    this.disposables = new Set(args)
   }
 
   // Public: Dispose all disposables added to this composite disposable.
@@ -44,7 +40,11 @@ module.exports = class CompositeDisposable {
   dispose() {
     if (!this.disposed) {
       this.disposed = true
-      this.disposables.forEach(disposable => disposable.dispose())
+      // traditional for is faster: https://jsbench.me/67kgn473ko/1
+      const disposablesArray = [...this.disposables]
+      for (let i = 0, len = disposablesArray.length; i < len; i++) {
+        disposablesArray[i].dispose();
+      }
       this.disposables = null
     }
   }
@@ -59,10 +59,14 @@ module.exports = class CompositeDisposable {
   //
   // * `...disposables` {Disposable} instances or any objects with `.dispose()`
   //   methods.
-  add() {
+  add(...args) {
     if (!this.disposed) {
-      for (const disposable of arguments) {
-        assertDisposable(disposable)
+      for (const disposable of args) {
+        if (!Disposable.isDisposable(disposable)) {
+          throw new TypeError(
+            "Arguments to CompositeDisposable.add must have a .dispose() method"
+          )
+        }
         this.disposables.add(disposable)
       }
     }
@@ -91,15 +95,3 @@ module.exports = class CompositeDisposable {
     }
   }
 }
-
-function assertDisposable(disposable) {
-  if (Disposable == null) {
-    Disposable = require("./disposable")
-  }
-
-  if (!Disposable.isDisposable(disposable)) {
-    throw new TypeError(
-      "Arguments to CompositeDisposable.add must have a .dispose() method"
-    )
-  }
-}

lib/disposable.js

@@ -1,14 +1,14 @@
 // Essential: A handle to a resource that can be disposed. For example,
 // {Emitter::on} returns disposables representing subscriptions.
-module.exports = class Disposable {
+export default class Disposable {
   // Public: Ensure that `object` correctly implements the `Disposable`
   // contract.
   //
   // * `object` An {Object} you want to perform the check against.
   //
   // Returns a {Boolean} indicating whether `object` is a valid `Disposable`.
   static isDisposable(object) {
-    return typeof (object != null ? object.dispose : undefined) === "function"
+    return Boolean(object) && (typeof object.dispose === "function")
   }
 
   /*

lib/emitter.js

@@ -1,5 +1,5 @@
-const Disposable = require("./disposable")
-const CompositeDisposable = require("./composite-disposable")
+import Disposable from "./disposable"
+import CompositeDisposable from "./composite-disposable"
 
 // Essential: Utility class to be used when implementing event-based APIs that
 // allows for handlers registered via `::on` to be invoked with calls to
@@ -28,7 +28,7 @@ const CompositeDisposable = require("./composite-disposable")
 //   }
 // }
 // ```
-class Emitter {
+export default class Emitter {
   static onEventHandlerException(exceptionHandler) {
     if (this.exceptionHandlers.length === 0) {
       this.dispatch = this.exceptionHandlingDispatch
@@ -212,22 +212,20 @@ class Emitter {
   //   for the same name will be invoked.
   // * `value` Callbacks will be invoked with this value as an argument.
   emit(eventName, value) {
-    const handlers =
-      this.handlersByEventName && this.handlersByEventName[eventName]
+    const handlers = this.handlersByEventName?.[eventName]
     if (handlers) {
       // create a copy of `handlers` so that if any handler mutates `handlers`
       // (e.g. by calling `on` on this same emitter), this does not result in
       // changing the handlers being called during this same `emit`.
       const handlersCopy = handlers.slice()
-      for (let i = 0; i < handlersCopy.length; i++) {
+      for (let i = 0, len = handlersCopy.length; i < len; i++) {
         this.constructor.dispatch(handlersCopy[i], value)
       }
     }
   }
 
   emitAsync(eventName, value) {
-    const handlers =
-      this.handlersByEventName && this.handlersByEventName[eventName]
+    const handlers = this.handlersByEventName?.[eventName]
     if (handlers) {
       const promises = handlers.map(handler =>
         this.constructor.dispatch(handler, value)
@@ -243,18 +241,18 @@ class Emitter {
 
   listenerCountForEventName(eventName) {
     const handlers = this.handlersByEventName[eventName]
-    return handlers == null ? 0 : handlers.length
+    return handlers?.length ?? 0
   }
 
   getTotalListenerCount() {
     let result = 0
-    for (let eventName of Object.keys(this.handlersByEventName)) {
-      result += this.handlersByEventName[eventName].length
+    const eventNames = Object.keys(this.handlersByEventName)
+    for (let i = 0, len = eventNames.length; i < len; i++) {
+      result += this.handlersByEventName[eventNames[i]].length
     }
     return result
   }
 }
 
 Emitter.dispatch = Emitter.simpleDispatch
 Emitter.exceptionHandlers = []
-module.exports = Emitter

lib/event-kit.js

@@ -1,3 +1,3 @@
-exports.Emitter = require("./emitter")
-exports.Disposable = require("./disposable")
-exports.CompositeDisposable = require("./composite-disposable")
+export { default as Emitter } from "./emitter";
+export { default as Disposable } from "./disposable"
+export { default as CompositeDisposable } from "./composite-disposable"

package.json

@@ -3,8 +3,11 @@
   "version": "2.5.3",
   "description": "Simple library for implementing and consuming evented APIs",
   "main": "./dist/event-kit",
+  "bundle": "./dist/event-kit.bundle.js",
   "scripts": {
-    "build": "cross-env BABEL_KEEP_MODULES=false babel lib --out-dir dist --delete-dir-on-start",
+    "babel": "cross-env BABEL_KEEP_MODULES=false babel lib --out-dir dist --delete-dir-on-start",
+    "bundle": "cross-env PARCEL_ENV=true cross-env NODE_ENV=production parcel build --target bundle lib/event-kit.js",
+    "build": "npm run babel && npm run bundle",
     "docs": "joanna-tello -o api.json package.json lib",
     "prepublish": "npm run build && npm run docs",
     "test": "jasmine-focused --captureExceptions --forceexit spec"
@@ -23,6 +26,17 @@
     "babel-preset-atomic": "^3.0.1",
     "cross-env": "^7.0.3",
     "jasmine-focused": "^1.0.7",
-    "joanna": "https://github.com/aminya/joanna"
+    "joanna": "https://github.com/aminya/joanna",
+    "parcel": "2.0.0-nightly.495"
+  },
+  "targets": {
+    "bundle": {
+      "context": "electron-renderer",
+      "engines": {
+        "electron": ">=6.x"
+      },
+      "outputFormat": "commonjs",
+      "isLibrary": true
+    }
   }
 }