JavaScript Type Promotion.

Usage

// ES5
var promote = require("promote");

// ES6
import {promote} from "promote";

promote(obj: object, promotype: callable, opts?: object): Promise

• obj: object
• An object, not undefined or null
• promotype: callable
• The type to which the given object should be promoted to
• opts: object
  • unsafe: boolean = false
  • true = Also allow promotion for incompatible types
  • strict: boolean = false
  • true = The object will be checked if it's already an instance of the given type

promoteSync(obj: object, promotype: callable, opts?: object): boolean

• obj: object
• @see promote()
• promotype: callable
• @see promote()
• opts: object
• @see promote()
  • silent: boolean = false
  • true = No exceptions will be thrown

Function bind (ES7)

let thing = new Thing();
thing.do();

thing::promote(SuperThing).then(() => {
  thing.superDo();
});

if (thing::promoteSync(SuperThing)) {
  thing.superDo();
}

Examples

One-Two

import {promote} from "promote";

function printName(obj: object): void {
  console.log(obj.name);
  console.log("  name:", obj.getName());
}

class One {
  name: string;
  constructor(name: string) {
    this.name = name;
  }
  getName() {
    return this.name;
  }
}

class Two extends One {
  getName() {
    return `${this.name}²`;
  }
}

let foo = {name: "foo"};
(promote(foo, Two)
  .then(printName)
  .catch(console.error)
);

let bar = new One("bar");
(bar::promote(Two)
  .then(printName)
  .catch(console.error)
);

> babel-node examples/one-two
foo
  name: foo²
bar
  name: bar²

HTTP server with promoted response

import {Server, ServerResponse} from "http";
import {promoteSync} from "promote";

class HttpResponse extends ServerResponse {
  writeHeading(title: string) {
    this.writeHead(200, {
      "Content-Type": "text/html",
    });
    this.end(`<h1>${title}</h1>`);
  }
}

class HttpServer extends Server {
  constructor(requestListener?: callable) {
    super((req, res) => {
      res::promoteSync(HttpResponse);
    });
    if (typeof requestListener === "function") {
      this.on("request", requestListener);
    }
  }
}

let server = new HttpServer((req, res) => {
  res.writeHeading("Hello World");
});
server.listen(8080, () => {
  console.log("Server running at http://localhost:8080/");
});

> babel-node examples/http
Server running at http://localhost:8080/