Simple pattern used for parallel async.
Finisher is a simple control flow tool that allows you to invoke a function after running multiple async operations in parallel.
npm install finisher
var finisher = require'finisher';// Create a wait function.// Wrap all your async callbacks within this functionvar wait = finisherdone;// Do async stuffdoSomethingAsyncwait// Do stuffdoSomethingAsyncwait// Do somethingdoSomethingAsyncwait// Do something else// This will get called after all the callbacks have finished// Called after all async operations have completed.
Finisher returns a wait function that will increment an internal counter when invoked. You must pass a callback to the wait function. The wait function returns a special function that will invoke the wait functions's callback and decrement the internal counter.
Once the internal counter reaches zero again (it starts at zero), then the finisher's callback will be invoked (known as the 'done' function). If the wait function is never called, then the done function is invoked on the next event loop. This allows you to expect execution to continue to flowing even if there are no parallel operations queued.
Check out the source code to get a better understanding; it's very a small lib.
Note: you can name these functions anything you like of course; 'wait' and 'done' are just recommended conventions.