invoke.js

invoke is a dead simple asynchronous flow control micro-library. Sequential (.then) and parallel (.and) async functions can be chained into simple steps:

invoke(function (data, callback) {
  // I'm an async function!
}).and(function (data, callback) {
  // I am too! I execute in parallel with the first function.
}).then(function (data, callback) {
  // I run after both of the parallel functions have called back. Their results
  // are passed to me as an array via the data arg.
}).rescue(function (err) {
  // I'll be invoked if any functions in the call chain call back with an error.
}).end(initialData, function (data) {
 // Calling .end initiates invocation of the set of chained steps. The final result
 // is passed to this callback.
});

Why?

Because I can.

This library is an experiment in flow control, chained APIs, and minimal JS syntax (yes, I skipped all those semi-colons on purpose).

Usage

invoke can be installed via npm:

npm install invoke

The API is exposed as a single function that generates a chainable Invocable object.

var invoke = require('invoke');

invoke(function (data, callback) {
  somethingAsync(function (err, results) {
    callback(err, results);
  });
}).then(function (data, callback) {
  // and so forth

Take a look at the examples.

Chainable methods on an Invocable:

then(func)

Adds a function as a sequential step. This function will not be invoked until all previous steps have called back, and later steps will not be invoked until this function calls back.

func is invoked with:

• data - The result of the previous step. If the previous step was sequential, this is the value passed by the previous step’s callback. If the previous step was parallel, it is an array of the values passed by the callbacks of the parallel functions.
• callback(err, results) - Function to be invoked once with either an error or the results of this step.

and(func)

Adds a function as a parallel step. This function will not be invoked in parallel with any other functions chained with .and immediately before or immediately after this .and call.

func is invoked with:

• data - The result of the previous step. If the previous step was sequential, this is the value passed by the previous step’s callback. If the previous step was parallel, it is an array of the values passed by the callbacks of the parallel functions.
• callback(err, results) - Function to be invoked once with either an error or the results of this step.

rescue(func)

Adds an error handler. This function will be invoked once if any function in the call chain calls back with an error.

func is invoked with

• err - The error.

end(initialValue, callback)

Adds a final callback and initiates invocation of the function steps defined in the chain. initialValue is the initial value passed as the first argument into the first function step.

callback is invoked with

• data - The result of the previous (final) step. If the previous step was sequential, this is the value passed by the previous step’s callback. If the previous step was parallel, it is an array of the values passed by the callbacks of the parallel functions.

Testing

Install dev dependencies

$ npm install -d
$ npm test

Building & Linting

$ npm run-script build

License

invoke.js is MIT licensed. See LICENSE.