警告：承诺以非错误被拒绝：[object GeolocationPositionError]

Question

[尝试从用户的浏览器获取地理位置时，如果用户拒绝了许可或阻止了浏览器共享位置，我们会从Bluebird收到控制台警告，内容为：Warning: a promise was rejected with a non-error: [object GeolocationPositionError]。

但是，当我们捕获并记录错误时，会收到错误消息：User denied geolocation prompt，它来自地理位置API的GeolocationPositionError。我想象在其他两种情况下将返回GeolocationPositionError（内部位置错误或超时）的情况下，将记录相同的警告。

那么为什么我们会收到该控制台警告，以及如何正确处理它？

这里是处理浏览器导航器和地理位置的代码：

import Promise from 'bluebird';

function getUserLocation() {
  return new Promise(function(resolve, reject) {
    if (navigator && navigator.geolocation) {
      navigator.geolocation.getCurrentPosition(resolve, reject);
    } else {
      // Browser does not support geolocation at all
      reject(new Error('Geolocation is unsupported'));
    }
  });
}

Answer 1

阅读有关警告消息的Bluebird文档："Warning: a promise was rejected with a non-error"，我发现问题是GeolocationPositionError不是Javascript Error实例，这显然是Bluebird所期望的。因此，相反，自定义reject()回调以将GeolocationPositionError显式转换为Error可以解决对于GeolocationPositionError的任何情况的控制台警告和错误处理。

import Promise from 'bluebird';

export function getUserLocation() {
  return new Promise(function(resolve, reject) {
    if (navigator && navigator.geolocation) {
      navigator.geolocation.getCurrentPosition(
        resolve,
        (geolocationPositionError) => { // reject
          // Note: must explicitly cast the `GeolocationPositionError` as an Error instance since bluebird explicitly expects a javascript Error object
          // see http://bluebirdjs.com/docs/warning-explanations.html#warning-a-promise-was-rejected-with-a-non-error
          // and `GeolocationPositionError` is not an Error instance, see https://developer.mozilla.org/en-US/docs/Web/API/GeolocationPositionError
          return reject(new Error(geolocationPositionError));
        }
      );
    } else {
      // Browser does not support geolocation at all
      reject(new Error('Geolocation is unsupported'));
    }
  });