Callbacks from nested functions

Question

I have a function such as this:

//parent function
function myFirstFunction(param1, callback) {
 //outside inside
 mySecondFunction(param1,function(error,result){
 if(error){ //should return 'error in mySecondFunction' to whoever called this }
 else{
 myThirdFunction(error2,result2){
 if(error2){ //should return 'error in myThirdFunction' to whoever called this }
 else{ //should return 'Success in myThirdFunction' to whoever called this }
 });
 }
 });
});

I then call this function such as this:

myFirstfunction(p1, function(e,r){
 if(e){ console.log('The error returned is : ' + e) };
 else{console.log('Success! The message returned should be Success in myThirdFunction. Is it? ' + r );}
});

I am confused where to put the callbacks inside of nested functions. For instance if I didn't have any nested functions I would simply return callback(null, 'Success in first function') in the body. How can I return these messages back to whatever called them so they know if there were any errors or if it made it all the way to the 3rd function successfully?

Answer 1

You're doing everything right! You can just call the callback as you passed it in myFirstFunction with each error i.e.

 function myFirstFunction(param1, callback) {
 //outside inside
 mySecondFunction(param1,function(error,result){
 if(error){
 callback("error in mySecondFunction");
 }
 else{
 myThirdFunction(error2,result2){
 if(error2){ 
 callback("error in myThirdFunction");
 }
 else{ 
 callback(null,result2);//I'm not sure what data you want here
 }
 });
 }
 });
});