CODEWITHSUNDEEP
javascriptfunctioncallback
ulisse0744
ulisse0744

Reputation: 21

There is any difference between callback function and calling a function inside another function?

Let's take this example:

function foo(callback){
        callback();
        baz();
  }

  function baz() {
        console.log('Hello from baz');  
   }

   foo(baz);

It looks like they are doing the same task. Or callback and calling a function inside another function are the same thing?

Upvotes: 0

Views: 1611

Answers (3)

ControlAltDel
ControlAltDel

Reputation: 35011

Except you aren't using the callback the way callbacks are supposed to be used. Callbacks are supposed to get the interim results from a previous function. Here's an example

function add (a, b) {
  return a + b;
}

function subtract (a, b) {
  return a - b;
}

This is the callback

function doLater (val) {
  if (val > 0) {
    console.log("positive");
  } else if (val ==) {
    console.log("zero");
  } else console.log ("negative");
}

function doOp (a, b, mathOp, callback) {
  var res = mathOp(a,b);
  callback(res);
}

doOp (2,3, add, doLater);

vs.

doOp (2,3,subtract, doLater);

Upvotes: 2

Empiire
Empiire

Reputation: 565

In your example, both approaches will do the same.

However, you can pass function as parameters, that are not in the functions scope. E.g.

function foo(callbackFn){
    callbackFn();
    // function test is undefined here, since it was declared in another scope 
}

function bar(){
    // test is only available in bar's scope
    function test(){
        console.log("test");
    }
    foo(bar);
}

Upvotes: 0

Apollo79
Apollo79

Reputation: 704

Basically, they are doing the same, but callbacks are very useful because you can call the same function with many different callbacks. That makes your foo function more reusable.

Upvotes: 2

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