CODEWITHSUNDEEP
javascript
markzzz
markzzz

Reputation: 47945

How to create a custom callback

I have a function that done some asynch operations :

function funcAsynch() {
    // asynch operations
}

well, I'd like calling this function, and declare a callback to execute when all asynch operations are finished.

Somethings like 

customCallback(funcAsynch(), function () { 
    alert("all asynch operations are finished") 
});

how can I do it?

Upvotes: 1

Views: 124

Answers (3)

I Hate Lazy
I Hate Lazy

Reputation: 48761

Define a parameter for your funcAsynch() function.

function funcAsynch(callback) {
    // asynch operations
    // invoke callback() when asynch is done
}

And pass the callback function to that parameter.

funcAsynch(function () { 
    alert("all asynch operations are finished");
});

Upvotes: 1

Andreas Louv
Andreas Louv

Reputation: 47099

A little helper function:

function asyncFn() {
  var readyList = [],
       isReady = false;

  function emitReady() {
    isReady = true;
    var i = 0,
        len = readyList.length;

    for ( ; i < len; i++ ) {
      emit( readyList[i] );
    }
  }
  function emit( fn ) {
    fn();
  }
  function ready( fn ) {
      if ( !isReady ) {
        readyList.push( fn );
      }
      else {
        emit( fn );
      }
    }

  return {
    ready: ready,
    emitReady: emitReady
  };
}

Usecase 1

function F() {
    var async = asyncFn();

    async.ready(function() {
        // Called when emitReady is called
    });

    async.emitReady();
}

Usecase 2

function customAsync() {
  var async = asyncFn();

  /*
    Async stuff going on here....
  */
  setTimeout(function() {
    async.emitReady();
  }, 500);

  return async;
}

function customCallback(def, callback) {
  def.ready(callback);
}


customCallback(customAsync(), function() {
  console.log("async is operated");
});

Just one approach...

Upvotes: 0

Jericho
Jericho

Reputation: 10953

function doSomething(callback) {
    // ...

    // Call the callback
    callback('stuff', 'goes', 'here');
}

function foo(a, b, c) {
    // I'm the callback
    alert(a + " " + b + " " + c);
}

doSomething(foo);

Upvotes: 1

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