Task

The @daiso-tech/core/task component provides a better alternative to Promise.

info

In the future the @daiso-tech/core/task component will provide support for structured concurrency.

Basic usage

The Task class is PromiseLike object that behaves similarly to regular Promise but executes only when awaited or when manually defered with the detach method.

Creating and executing

import { Task } from "@daiso-tech/core/task";

const task = new Task(async () => {
    // This will log when awaited
    console.log("2.");
    return await fetch("URL");
});

console.log("1.");
await task;
console.log("3.");

You can execute a Task without awaiting it:

import { Task } from "@daiso-tech/core/task";
import { TimeSpan } from "@daiso-tech/core/time-span";

const task = new Task(async () => {
    await Task.delay(TimeSpan.fromSeconds(1));
    console.log("2.");
    return await fetch("URL");
});

console.log("1.");
task.detach();
console.log("3.");
await Task.delay(TimeSpan.fromSeconds(2));

Adding middlewares

You can add middlewares to a Task. Refer to the @daiso-tech/core/hooks documentation for further information.

Through the constructor:

import { Task } from "@daiso-tech/core/task";

const task = new Task(async () => {
    return await fetch("URL");
}, [
    (args, next) => {
        console.log("Middleware 1");
        return next(...args);
    },
]);

await task;

Through the pipe method:

import { Task } from "@daiso-tech/core/task";

const task = new Task(async () => {
    return await fetch("URL");
}).pipe((args, next) => {
    console.log("Middleware 1");
    return next(...args);
});

await task;

Through the pipeWhen method:

import { Task } from "@daiso-tech/core/task";

const task = new Task(async () => {
    return await fetch("URL");
}).pipeWhen(true, (args, next) => {
    console.log("Middleware 1");
    return next(...args);
});

await task;

Static methods

Task provides static helper methods (all, allSettled, race, and any) that mirror their Promise counterparts, but with lazy execution behavior. Like individual Task instances, these methods only evaluate when awaited or when their detach method is explicitly called.

The are additional static method, delay and fromCallback.

• The delay method creates a Task that resolves after a given time:

  import { Task } from "@daiso-tech/core/task";
  import { TimeSpan } from "@daiso-tech/core/time-span";
  
  // Will wait 1 second
  await Task.delay(TimeSpan.fromSeconds(1));
  console.log("DONE");

  You can provide an AbortSignal to aborat the delay:

  import { Task } from "@daiso-tech/core/task";
  import { TimeSpan } from "@daiso-tech/core/time-span";
  
  const abortController = new AbortController();
  abortController.abort("No need to wait");
  
  // Will not wait for the delay
  await Task.delay(TimeSpan.fromSeconds(1), abortController.signal);
  console.log("DONE");

• The fromCallback is convience method used for wrapping Node js callback functions with a Task.

  import { Task } from "@daiso-tech/core/task";
  import { readFile } from "node:fs";
  
  const task = Task.fromCallback<Buffer | string>((resolve, reject) => {
      readFile("FILE_PATH", (err, data) => {
          if (err !== null) {
              reject(err);
              return;
          }
          resolve(data);
      });
  });
  const file = await task;
  console.log(file);

Further information

For further information refer to @daiso-tech/core/task API docs.