function-done

Handles completion and errors for sync, callbacks, promises, observables and streams.

Usage no npm install needed!

<script type="module">
  import functionDone from 'https://cdn.skypack.dev/function-done';
</script>

README

function-done

build status

Handles completion and errors for standard functions, generators, async functions, callbacks, promises, observables, child processes and streams.

Will run call the function on nextTick. This will cause all functions to be async.

Why?

You are given a callback and want to know when it's finished. I found it useful for a testing framework. Specifically, I needed to know when the test had finished.

asyncDone Fork

This is a fork of asyncDone with sync and generator functionality added. Thanks for the hard work at gulpjs/async-done

API

funcDone(fn, callback)

Takes a function to execute (fn) and a function to call on completion (callback).

fn([done])

Optionally takes a callback to call when async tasks are complete. If done parameter is not defined and function doesn't return Stream, Child Process, Promise, Observable, and is not a generator function, the function is assumed to be synchronous

Usage

Successful completion

Callback


// Async example
funcDone(function(done){

  // do async things
  setTimeout(function() {

    // Call done function on finish
    done(null, 2);
  }, 10);
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Stream

funcDone(function(){

 // return Stream. emit end of finish
 var read = fs.createReadStream(exists);
 return read.pipe(new EndStream());
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Generator

funcDone(function* (){
  function delay(time) {
    return new Promise(function (resolve) {
       setTimeout(resolve, time);
    });
  }

  // yield as many times as necessary
  yield delay(10);
  yield delay(100);
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Promise

funcDone(function (){
  function delay(time) {
    return new Promise(function (resolve) {
       setTimeout(resolve, time);
    });
  }

  // return a Promise from the function
  return delay(10).then(function() {
    return delay(100);
  });
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Async Function

funcDone(async function (){
  function delay(time) {
    return new Promise(function (resolve) {
       setTimeout(resolve, time);
    });
  }

  // return a Promise from the function
  await delay(10);
  await delay(100);
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Child Process

funcDone(function(){

  // return child process from the function
  return cp.exec('echo hello world');
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Sync

funcDone(function(){
  return 2
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Failed completion

Callback


// Async example
funcDone(function(done){

  // do async things
  setTimeout(function() {

    // Call done function on finish
    done(new Error('An Error Occurred'));
  }, 10);
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Stream

funcDone(function(){

 // return Stream. emit end of finish
 var read = fs.createReadStream(notExists);
 return read.pipe(new EndStream());
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Generator

funcDone(function* (){
  throw new Error('Generator error');
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Promise

funcDone(function (){
  return Promise.reject(new Error('Rejected Promise'));
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Async Function

funcDone(async function (){
  throw new Error('Async Error');
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Child Process

funcDone(function(){

  // return child process error from the function
  return cp.exec('not-an-executable hello world');
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Sync

funcDone(function(){
  throw new Error('function error');
}, function(error, result){
  // `error` will be null on successful execution of the first function.
  // `result` will be the result from the first function.
});

Completion and Error Resolution

  • Sync function (function takes 0 params and doesn't return any of the below types)
    • Completion: function completes
    • Error: Error thrown
  • Callback called
    • Completion: called with null error
    • Error: called with non-null error
  • Stream or EventEmitter returned
  • Generator returned
    • Completion: function completes
    • Error: Error thrown
  • Child Process returned
  • Promise returned (Async Function)
  • Observable returned

callback(error, result)

If an error doesn't occur in the execution of the fn function, the callback method will receive the results as its second argument. Note: Observable and some streams don't received any results.

If an error occurred in the execution of the fn function, The callback method will receive an error as its first argument.

Errors can be caused by:

  • A thrown error
  • An error passed to a done callback
  • An error event emitted on a returned Stream, EventEmitter or Child Process
  • A rejection of a returned Promise
  • The onError handler being called on an Observable

License

MIT