Node.js Callback hell is a phenomenon that afflicts a JavaScript developer when he tries to execute multiple asynchronous operations one after the other.
An asynchronous function is one where some external activity must complete before a result can be processed; it is “asynchronous” in the sense that there is an unpredictable amount of time before a result becomes available. Such functions require a callback function to handle errors and process the result.
See the following example:-
getData(function(a){
getMoreData(a, function(b){
getMoreData(b, function(c){
getMoreData(c, function(d){
getMoreData(d, function(e){
...
});
});
});
});
});
There are following techniques to avoid callback hell:-
- Using Async.js
- Using Promises
- Using Async-Await
