Using java script promises for calling function once

Question

  var dataPromise= $q.defer();

  function getDataPromise(){
    return dataPromise.promise;
  }

  (function getData(){
    setTimeOut(
       function(){
          myPromise.resolve("data");
       }
      ,1000);
  })();

   getDataPromise().then(function(){alert("use old data");});

In this code "dataPromise" defined out of "getData" function scope, therefor new promise won't be created on each "getData" invocation.

"getData" will invoce once and "dataPromise" will hold the first invoke data, and won't be update.

I want to understand if this is promise anty-pattern? if so - what is the correct way to call async function once?

Answer 1

Here's how I would write it:

const dataPromise = $q(function(resolve) {
    setTimeOut(function() {
        resolve("data");
    }, 1000);
});

function getDataPromise() {
    return dataPromise;
}

getDataPromise().then(function(){alert("use old data");});