JS Promises - can't get it to work.

[fuzzybabybunny]

This is the first time I've tried writing a promise and I'm not quite able to get it to work. I need to have Googlemap's geocoder take a street address and return GPS coordinates, which is an async call.

I'm using this as a tutorial:

http://www.html5rocks.com/en/tutorials/es6/promises/#toc-javascript-promises

var geocode = new Promise(function(resolve, reject) {

  // async call to Google's Geocoder - takes street address
  // and returns GPS coordinates

  var address = "1600 Amphitheatre Pkwy, Mountain View, CA 94043";
  geocoder = new google.maps.Geocoder();
  if (geocoder) {
    geocoder.geocode({'address': address}, function(results, status) {
      if (status == google.maps.GeocoderStatus.OK) {
        if (results[0]) {
          console.log("got results!");
          var gpsPosition = {};
          gpsPosition.B = results[0].geometry.location['B'];
          gpsPosition.k = results[0].geometry.location['k'];
          console.log(gpsPosition);
        } else {
          alert("No results found");
        }
      } else {
        alert("Geocoder failed due to: " + status);
      }
    });
  }

  // this part just isn't working
  // what should go inside this if statement to check
  // if the async call worked and gpsPosition has been defined?

  if (!!gpsPosition.B /* everything turned out fine */) {
    resolve("Stuff worked!");
  }
  else {
    reject(Error("It broke"));
  }

});

geocode.then(function(result) {
  console.log(result); // "Stuff worked!"
}, function(err) {
  console.log(err); // Error: "It broke"
});

Help?

 

[fuzzybabybunny]

Bah, I just got it to work.

var geocode = new Promise(function(resolve, reject) {

  // async call to Google's Geocoder - takes street address
  // and returns GPS coordinates
  var address = "1600 Amphitheatre Pkwy, Mountain View, CA 94043";
  var gpsPosition = {};
  geocoder = new google.maps.Geocoder();
  if (geocoder) {
    geocoder.geocode({'address': address}, function(results, status) {
      if (status == google.maps.GeocoderStatus.OK) {
        if (results[0]) {
          console.log("got results!");
          gpsPosition.B = results[0].geometry.location['B'];
          gpsPosition.k = results[0].geometry.location['k'];
          console.log(gpsPosition);
          resolve(gpsPosition);
        } else {
          alert("No results found");
          reject(Error("It broke"));
        }
      } else {
        alert("Geocoder failed due to: " + status);
        reject(Error("It broke"));
      }
    });
  }

});

geocode.then(function(result) {
  console.log("This is the gpsPosition");
  console.log(result); // "logs the content of gpsPosition"
}, function(err) {
  console.log(err); // Error: "It broke"
});

So the steps:

1. Create a new Promise object and give it a name.
2. Inside of your Promise object goes your async code.
3. When your async code returns what you need, return that data inside of resolve();
4. When your async code fails, put an Error object inside of reject();
5. Outside of your Promise object, do nameOfPromise.then and you can grab the contents of resolve() with result (or whatever you named your "result" parameter).