Utilizing asynchronous JavaScript imports within exported classes

Question

Utilizing asynchronous JavaScript imports within exported classes

Currently, I have a package with async/dynamic exports that I import in the following manner:

(async function() {
  const libEd = await import("../../.cache/ed25519wars/index.js");
})();

I plan to re-expose certain functions from libEd within a class structure:

export class Something {
  static from_X() {
    return libEd.genFromX();
  }

  do_Y() {
    return libEd.doY();
  }
}

How can I achieve this?

Additional Information:

The package with async/dynamic exports is created using webpack to pack webassembly. I am unsure if modifications can be made to this aspect.
I have the flexibility to modify how I import the package.
We can also explore alternative methods to re-expose/group the functions instead of using a class.

javascript typescript class dynamic-import

Answer 1

Answer №1

Approaching this situation can be done in a couple of ways:

If there is no immediate need for the class instantiation, waiting for the library to load and then passing it to the class constructor would be the cleanest method. This ensures that the library is always defined within the class.
In cases where the class needs to be instantiated before fetching the library, methods within the class should handle scenarios when the library is not yet defined or loaded. To address this, you can use something like await myClassInstance.init() to retrieve the library. It is advisable to provide fallbacks for each method if the library is not loaded yet, such as returning an empty string or a dummy UI.

EDIT: A TypeScript example for option 1 has been added below:

interface MyLibrary {
  libraryMethod: () => void;
}

class ExampleClass {
  localLib: MyLibrary;

  constructor(lib: MyLibrary) {
    this.localLib = lib;
  }

  myClassMethod() {
    this.localLib.libraryMethod();
  }
}

async function run() {
  // Fetching the remote library first
  const myLibrary: MyLibrary | undefined = await import('/lib.js');

  // Adding a check for good practice
  if (!myLibrary) {
    throw Error('failed to fetch myLib');
  }

  // Creating an instance of the class using the downloaded library
  const myClassInstance = new ExampleClass(myLibrary);

  // Calling the class method knowing that the remote library is now available
  myClassInstance.myClassMethod();
}

Answer 2

Approaching this situation can be done in a couple of ways:

If there is no immediate need for the class instantiation, waiting for the library to load and then passing it to the class constructor would be the cleanest method. This ensures that the library is always defined within the class.
In cases where the class needs to be instantiated before fetching the library, methods within the class should handle scenarios when the library is not yet defined or loaded. To address this, you can use something like await myClassInstance.init() to retrieve the library. It is advisable to provide fallbacks for each method if the library is not loaded yet, such as returning an empty string or a dummy UI.

EDIT: A TypeScript example for option 1 has been added below:

interface MyLibrary {
  libraryMethod: () => void;
}

class ExampleClass {
  localLib: MyLibrary;

  constructor(lib: MyLibrary) {
    this.localLib = lib;
  }

  myClassMethod() {
    this.localLib.libraryMethod();
  }
}

async function run() {
  // Fetching the remote library first
  const myLibrary: MyLibrary | undefined = await import('/lib.js');

  // Adding a check for good practice
  if (!myLibrary) {
    throw Error('failed to fetch myLib');
  }

  // Creating an instance of the class using the downloaded library
  const myClassInstance = new ExampleClass(myLibrary);

  // Calling the class method knowing that the remote library is now available
  myClassInstance.myClassMethod();
}

Answer 3

Answer №2

After considering various options, I narrowed it down to three possible methods:

Following @Tim's method (which is the accepted answer): include the import in the class properties and use await at constructor time.

However, there may be a downside of overhead associated with storing the import in each instance.

awaiting in each method of the class to define the import locally:

export class Something {
  static async from_X() {
    const libEd = await loadLibProm();
    return libEd.genFromX();
  }

  async do_Y() {
    const libEd = await loadLibProm();
    return libEd.doY();
  }
}

Yet this results in the class API being entirely asynchronous and more cumbersome to work with.

Pre-loading the import at the start of the code and assuming that the loading will be completed when the class is called.

let libEd: typeof import("../../.cache/ed25519wars/index.js");
async function loadLibProm(): Promise<
  typeof import("../../.cache/ed25519wars/index.js")
> {
  libEd = await import("../../.cache/ed25519wars/index.js");
  return libEd;
}
loadLibProm(); // this somehow starts running the promise ?? wut ? Anyways that's what we want

export class Something {
  static from_X() {
    return libEd.genFromX();
  }

  do_Y() {
    return libEd.doY();
  }
}

Nonetheless, this approach requires improved error handling for cases where an instance of the class is created before the import is completed or after the import fails.

Answer 4

After considering various options, I narrowed it down to three possible methods:

Following @Tim's method (which is the accepted answer): include the import in the class properties and use await at constructor time.

However, there may be a downside of overhead associated with storing the import in each instance.

awaiting in each method of the class to define the import locally:

export class Something {
  static async from_X() {
    const libEd = await loadLibProm();
    return libEd.genFromX();
  }

  async do_Y() {
    const libEd = await loadLibProm();
    return libEd.doY();
  }
}

Yet this results in the class API being entirely asynchronous and more cumbersome to work with.

Pre-loading the import at the start of the code and assuming that the loading will be completed when the class is called.

let libEd: typeof import("../../.cache/ed25519wars/index.js");
async function loadLibProm(): Promise<
  typeof import("../../.cache/ed25519wars/index.js")
> {
  libEd = await import("../../.cache/ed25519wars/index.js");
  return libEd;
}
loadLibProm(); // this somehow starts running the promise ?? wut ? Anyways that's what we want

export class Something {
  static from_X() {
    return libEd.genFromX();
  }

  do_Y() {
    return libEd.doY();
  }
}

Nonetheless, this approach requires improved error handling for cases where an instance of the class is created before the import is completed or after the import fails.

Utilizing asynchronous JavaScript imports within exported classes

Answer №1

Answer №2

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