When anyone complains about the pain of callback functions, the usual recommendation is to use promises. Promises have been around for a number of years and there are a variety of promise libraries available for both Node and client scripting environments, with Q being a popular package for node.
Promises are useful, particularly when they destroy a pyramid of doom. But promises can’t un-butcher the code sliced into functions to meet the demands of an asynch API. Also, promises require shims to transform a function expecting a callback into a function returning a promise, which is what Q.nfcall will do in the following code.
ECMAScript 6 (a.k.a Harmony) introduces the yield keyword. Anyone with some programming experience in C# or Python (and a number of other languages, except Ruby) will already be familiar with how yield can suspend execution of a function and return control (and a value) to the caller. At some later point, execution can return to the point just after yield occurred. In ES6, functions using the yield keyword are known as generator functions and have a special syntax (function*), as the following code demonstrates...
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