jquery how to pass parameter to callback function into pipe

Question

I have the simple example below :

function firstFunction(){
  var d = jQuery.Deferred();
  // some very time consuming asynchronous code...
  setTimeout(function() {
    console.log('1');
    d.resolve();
  }, 1000);
  return d.promise();
}
function secondFunction(param){
  console.log('parm = '+param);
  var d = $.Deferred();
  setTimeout(function() {
    console.log('2');
    d.resolve();
  }, 10);
  return d.promise();
}

firstFunction().pipe(secondFunction('OK'));

Resulat : param = OK 2 1 I lose the sync between functions. How t can pass parameter to secondFunction into pipe with sync?

Community · Accepted Answer · 2017-05-23 12:07:31Z

1

Well, you need to do small change:

Your code will execute secondFunction immediately and pass the return value from executing it as the argument to firstFunction which is unlikely what you want.

Read the full answer: Javascript callback function with parameters

console.log = function(message) {
  $('body').append('<div>' + message + '</div>');
}

function firstFunction(){
  var d = jQuery.Deferred();
  // some very time consuming asynchronous code...
  setTimeout(function() {
    console.log('1');
    d.resolve();
  }, 1000);
  return d.promise();
}
function secondFunction(param){
  console.log('parm = '+param);
  var d = $.Deferred();
  setTimeout(function() {
    console.log('2');
    d.resolve();
  }, 10);
  return d.promise();
}

firstFunction().then(function() {
  secondFunction('OK')
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

edited May 23, 2017 at 12:07

CommunityBot

11 silver badge

answered Feb 24, 2016 at 15:52

Mosh Feu

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6 Comments

Bergi Over a year ago

Don't forget to return the promise from the callback

Bergi Over a year ago

That every asynchronous function should return a promise to be useful. In your case, the then callback is missing the return, so you can't chain anything onto it.

Bergi Over a year ago

Oh wait, you're still using pipe?! Replace it with then immediately, it's been deprecated for years now!

Mosh Feu Over a year ago

@Bergi I just followed by the question :) But I was updated my answer.. Thanks.. About your comment, I don't understand. Do you mean that I should add return ?? after the line secondFunction('OK')? If so, what I need to return?

Mosh Feu Over a year ago

@collo21 My pleasure ;) Good luck.

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