Node.js v9.6.1 Documentation.It is also called asynchronously from the embedder API emitDestroy().fn The function to call in the execution context of this async resource. If the simplest case for asynchrony is calling functions that return promises, then the next step is defining your own function which passes a promise on.Its a standard feature in the most recent versions of Node.js, so its ready for you out of the box. Also, I found this question on SO ("How do I create a non-blocking asynchronous function in node.js?") interesting.Will print 42 to the console asynchronously. In particular process.nextTick fires after the current eventloop callstack is empty. One common Node.js issue related to using callbacks is calling them more than once. Typically, a function provided by a package to do something asynchronously is designed to expect a function as its last argument, which is called when the asynchronous task has been completed Callback is similar to a function but it operates asynchronously. In other words, the callback function is always called immediately after the completion of an agreed task. In Node.