CODEWITHSUNDEEP
javascriptnode.js
shriek
shriek

Reputation: 5823

Passing scope of a function to the callback function

In node let's say I have the following code:-

function readDirectory(callback){
    fs.readdir('./', filterList);
}

function filterList(err,data){
    //callback is undefined
    if(err) callback(err);
    callback();
}

readDirectory(function(){
    console.log("Hi");
}

But the following works if I define function inside the readDirectory itself because it's in the same scope:-

function readDirectory(callback){
    fs.readdir('./', function(err,data){
        if(err) callback(err);
        callback();
    });
}

readDirectory(function(){
    console.log("Hi");
}

So my question is, is there a way to pass the scope of readDirectory to the callback function that's defined outside?

Upvotes: 0

Views: 68

Answers (1)

Felix Kling
Felix Kling

Reputation: 816462

So my question is, is there a way to pass the scope of readDirectory to the callback function that's defined outside?

No, JavaScript has lexical scope. However, you can make filterList accept a callback:

function readDirectory(callback){
    fs.readdir('./', filterList(callback));
}

function filterList(callback) {
  return function(err,data){
    if(err) callback(err);
    callback();
  };
}

Upvotes: 2

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