Replace $.Deferred with plain JavaScript Promise

Question

I am working on a Chrome extension which has no reason to use jQuery, but which does have a reason to use the meteor-ddp.js script, which uses jQuery only in order to access the $.Deferred functionality. It only uses three methods: reject, resolve and promise:

var conn = new $.Deferred();
//...
conn.reject(err);
//...
conn.resolve(data);
//...
return conn.promise();

Now that JavaScript has its own native Promise objects, it seems unnecessary to include at least 69 KB of jQuery slim.min.js just to provide a promise feature.

It would be great if someone with more experience than I have of jQuery and promises could explain how the $.Deferred functionality works, and how it could be replaced with native Promises.

note that you will need a fallback library for some browsers caniuse.com/#feat=promises — charlietfl
– charlietfl, Commented Sep 18, 2016 at 0:55
Which part do you not understand? As it stands, the question is too broad, you're asking for someone to implement deferred using Promise without giving it a try. Give it a try, and then ask a more focused question. api.jquery.com/jquery.deferred — Ruan Mendes
– Ruan Mendes, Commented Sep 18, 2016 at 1:15
The script in your link does not require jQuery, and does not use $.Deferred ? — adeneo
– adeneo, Commented Sep 18, 2016 at 1:26

Alex · Accepted Answer · 2016-09-18 01:09:47Z

8

This would be the equivalent of your code sample in es6:

return new Promise((resolve, reject) => {
  // ...
  reject(err);
  // ...
  resolve(data);
});

answered Sep 18, 2016 at 1:09

Alex

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