Promise Example

getLocation.js

/**
 * @example 
 * 
 * import {getLocation} from './services/getLocation';
 * getLocation().then(res => {
 *     console.log(res);
 * });
 *
 * @returns {Promise<any>}
 */
export function getLocation() {
    return new Promise(function(resolve, reject) {
        if ("geolocation" in navigator) {
            navigator.geolocation.getCurrentPosition(function (position) {
                resolve(position.coords.latitude, position.coords.longitude);
            });
        } else {
            reject(false);
        }
    });
}

promise-example.js

var promise = new Promise(function(resolve, reject) {
  // do a thing, possibly async, then…

  var request = new XMLHttpRequest();
  request.open('GET', 'https://www.reddit.com/r/webdev/top.json', true);

  request.onload = function() {
    if (this.status >= 200 && this.status < 400) {
      // Success!
      resolve(JSON.parse(this.response));
    } else {
      // We reached our target server, but it returned an error
      reject("Error");
    }
  };

  request.onerror = function() {
    // There was a connection error of some sort
  };
  
  request.send();
});

promise.then(function(webDevTop) {
  console.log(webDevTop);
}, function(err) {
  console.log(err); // Error: "It broke"
});