Like async.auto but with Promises, less boilerplate, and proper typechecking.

Run a collection of async functions ("tasks") in parallel. Any task can await the resolution of any other task by name: await this.nameOfFunction() Behind the scenes, task functions are replaced with shims so that each task function is invoked exactly once. Once all tasks have resolved, the return promise will resolve with a dictionary of the unwrapped return values from each task.

Type declarations require TypeScript 2.8, which at the time of writing, is still in development. npm install typescript@next

Example

Based on an example from async's documentation

import {auto} from '@cspotcode/promise-auto';

const results = await auto({
    async getData() {
        // async code to get some data
        return backend.getSomeData();
    },
    async makeFolder() {
        // async code to create a directory to store a file in
        // this is run at the same time as getting the data
        const folder = await backend.makeFolder();
        return folder;
    },
    async writeFile() {
        // once there is some data and the directory exists,
        // write the data to a file in the directory
        const file = await backend.writeFileInDirectory(await this.makeFolder(), await this.getData());
        return file;
    },
    async emailLink() {
        // once the file is written let's email a link to it...
        // results.write_file contains the filename returned by write_file.
        return sendEmail({'file': await this.writeFile(), 'email': '[email protected]'});
    }
});
console.log('results = ', results);

Why this?

Normally I avoid custom bindings of this, instead favoring positional arguments. In this case, this is more compatible with type inference, so it should give you better tab completion and static analysis. I also pass the same object as an argument to each task, so you can use whichever you prefer.

    async foo(others) {
        // both of these are equivalent
        await this.bar;
        await others.bar;
    }

TypeScript Declarations

This library includes bundled TypeScript type declarations. Enable "moduleResolution": "node" in your tsconfig.json and it will work automatically. Editors such as VSCode can even use these declarations to give you tab completion and documentation tooltips in your plain JavaScript projects.