deferring return of $.getJSON with async set to false

Question

I have attempted various solutions I have seen in other questions, but am not successfully logging data.ip.

When I log foo I only return undefined. Why is the ip property not being logged with async set to false?

TY

$.ajaxSetup({
  async: false
});

var getIp = function() {
  var ip;
  $.getJSON('//freegeoip.net/json/?callback=?', function(data) {
    ip = data.ip;
  });
  return ip;
}

var foo = getIp();
console.log(foo);

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

Never, ever, ever set `async` to `false`. It will seriously harm the performance of your web page. — Liam, Feb 09 '18 at 10:37
**Don't use `async:false`** Use the asynchronous callback pattern properly — Rory McCrossan, Feb 09 '18 at 10:37
$.getJSON does not accept `async: false` as per https://stackoverflow.com/questions/2765411/is-it-possible-to-set-asyncfalse-to-getjson-call — Faizuddin Mohammed, Feb 09 '18 at 10:39
@FaizuddinMohammed You are aware the next answer down shows you how to use `$.getJSON` with `async:false`? — George, Feb 09 '18 at 10:41
https://api.jquery.com/jQuery.getJSON/ also does not list `async: false` anywhere — Faizuddin Mohammed, Feb 09 '18 at 10:44
@FaizuddinMohammed Please stop and read the next answer down from the [link you posted](https://stackoverflow.com/a/6676835/2315360). — George, Feb 09 '18 at 10:48

messerbill · Accepted Answer · 2018-02-09T10:40:50.143

You not implementing AJAX correctly. I changed your function so that it will return a Promise (note the return keywords in the function). Afterwards inside .then() you can pass a callback function which will be executed once the Ajax has finished.$.getJSON() is an implementation of Ajax (http://api.jquery.com/jquery.ajax/)

NOTE:

I strongly recommend NOT to use async: false inside any xhr / Ajax due to it will slow down your website. Better use the code below:

var getIp = function() {
  var ip;
  return $.getJSON('//freegeoip.net/json/?callback=?', function(data) {
    return data.ip;
  });
}

getIp().then(function(res) {
  console.log(res);
})

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

deferring return of $.getJSON with async set to false

1 Answers1