Initial implementation, README and metadata

.gitignore

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+dist/*
+!dist/*.d.ts
+node_modules/
+.DS_Store
+Thumbs.db
+*.log

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2018 Andy Wermke
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# Typed-Emitter
+
+Strictly typed event emitter interface for **TypeScript 3**.
+
+Code size: Zero bytes - Just the typings, no implementation. Use the default event emitter of the `events` module in node.js or bring your favorite implementation when writing code for the browser.
+
+
+## Installation
+
+```sh
+$ npm install typed-emitter
+
+# Using yarn:
+$ yarn add typed-emitter
+```
+
+
+## Usage
+
+```ts
+import EventEmitter from "events"
+import TypedEmitter from "typed-emitter"
+
+// Define your emitter's types like that:
+// Key: Event name; Value: Listener function signature
+interface MessageEvents {
+  error: (error: Error) => void,
+  message: (body: string, from: string) => void
+}
+
+const messageEmitter = new EventEmitter() as TypedEmitter<MessageEvents>
+
+// Good 👍
+messageEmitter.emit("message", "Hi there!", "no-reply@test.com")
+
+// TypeScript will catch those mistakes ✋
+messageEmitter.emit("mail", "Hi there!", "no-reply@test.com")
+messageEmitter.emit("message", "Hi there!", true)
+
+// Good 👍
+messageEmitter.on("error", (error: Error) => { /* ... */ })
+
+// TypeScript will catch those mistakes ✋
+messageEmitter.on("error", (error: string) => { /* ... */ })
+messageEmitter.on("failure", (error: Error) => { /* ... */ })
+```
+
+## Why another package?
+
+The interface that comes with `@types/node` is not type-safe at all. It does not even offer a way of specifying the events that the emitter will emit...
+
+The `eventemitter3` package is a popular event emitter implementation that comes with TypeScript types out of the box. Unfortunately there is no way to declare the event arguments that the listeners have to expect.
+
+There were a few other examples of type-safe event emitter interfaces out there as well. They were either not published to npm, had an inconsistent interface or other limitations.
+
+
+## License
+
+MIT

index.d.ts

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+type Arguments<T> = [T] extends [(...args: infer U) => any]
+  ? U
+  : [T] extends [void] ? [] : [T]
+
+/**
+ * Type-safe event emitter.
+ *
+ * Use it like this:
+ *
+ * interface MyEvents {
+ *   error: (error: Error) => void
+ *   message: (from: string, content: string) => void
+ * }
+ *
+ * const myEmitter = new EventEmitter() as TypedEmitter<MyEvents>
+ *
+ * myEmitter.on("message", (from, content) => {
+ *   // ...
+ * })
+ *
+ * myEmitter.emit("error", "x")  // <- Will catch this type error
+ */
+interface TypedEventEmitter<Events> {
+  addListener<E extends keyof Events> (event: E, listener: Events[E]): this
+  on<E extends keyof Events> (event: E, listener: Events[E]): this
+  once<E extends keyof Events> (event: E, listener: Events[E]): this
+  prependListener<E extends keyof Events> (event: E, listener: Events[E]): this
+  prependOnceListener<E extends keyof Events> (event: E, listener: Events[E]): this
+
+  removeAllListeners<E extends keyof Events> (event: E): this
+  removeListener<E extends keyof Events> (event: E, listener: Events[E]): this
+
+  emit<E extends keyof Events> (event: E, ...args: Arguments<Events[E]>): boolean
+  eventNames (): (keyof Events)[]
+  listeners<E extends keyof Events> (event: E): Function[]
+  listenerCount<E extends keyof Events> (event: E): number
+
+  getMaxListeners (): number
+  setMaxListeners (maxListeners: number): this
+}
+
+export default TypedEventEmitter

package.json

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+{
+  "name": "typed-emitter",
+  "version": "0.1.0",
+  "license": "MIT",
+  "description": "Strictly typed event emitter interface for TypeScript 3.",
+  "author": "Andy Wermke (https://github.com/andywer)",
+  "repository": "github:andywer/typed-emitter",
+  "keywords": [
+    "event",
+    "emitter",
+    "typescript",
+    "interface"
+  ],
+  "peerDepedencies": {
+    "typescript": ">= 3.0"
+  }
+}