Back to back promise, how to determine which branch to return to promise-CodePudding

Just learning javascript soon, there is a call based on callback style, want to put him into a style based on the Promise of

 
FunA (res=& gt; {
If (res) 
FunIf ({()=& gt; {
The console. The log (' in the if the callback); 
}) 
The else 
FunElse (()=& gt; {
The console. The log (' in the else callback '); 
}) 
});

I am such a turn (assuming the promise with the same style) :

 
FunA (). Then (res=& gt; {
If (res) 
Return funIf ();//if the branch of Promise 
The else 
Return funElse ();//the else branch Promise 
}). Then (()=& gt; {
//here is how do I know which branch to come over? 
The console. The log (' in the if or else? '); 
});

I want to ask is, I in the back then, how can you know, this is the inside of the front then which branch?
Or, I should not use this model?

CodePudding user response:

 
FunA (). Then (res=& gt; {
If (res) 
Return funIf ();//if the branch of Promise 
The else 
Return funElse ();//the else branch Promise 
}). Then ((previousReturn)=& gt; {//& lt;======
//here is how do I know which branch to come over? 
The console. The log (' in the if or else? ', previousReturn);//a then the return value will be the next then get, can be judged according to the 
});

CodePudding user response:

Really want to have this kind of demand, the simplest is on your return if or else, the additional definitions or attach a label,