Drop node 8 support

.travis.yml

@@ -3,7 +3,7 @@ language: node_js
 node_js:
   # we recommend testing addons with the same minimum supported node version as Ember CLI
   # so that your addon works for all apps
-  - "8"
+  - "10"
 
 addons:
   chrome: stable

addon/types.ts

@@ -0,0 +1,38 @@
+import Mix from '@ember/polyfills/types';
+
+export type Nullable<T> = T | null | undefined;
+
+export type PlainObject<T = string | number | boolean> = {
+  [key: string]: T | PlainObject<T> | PlainObject<T>[];
+}
+
+export type PlainHeaders = {
+  [key: string]: string;
+}
+
+export type Method =
+  | 'HEAD'
+  | 'GET'
+  | 'POST'
+  | 'PUT'
+  | 'PATCH'
+  | 'DELETE'
+  | 'OPTIONS';
+
+export type AjaxOptions = {
+  url: string;
+  type: Method;
+  data?: PlainObject<string> | BodyInit;
+  headers?: PlainHeaders;
+};
+
+export type Credentials = 'omit' | 'same-origin' | 'include';
+
+export type FetchOptions = Mix<
+  AjaxOptions,
+  { body?: BodyInit | null; method?: Method, credentials: Credentials }
+>;
+
+export function isPlainObject(obj: any): obj is PlainObject {
+  return Object.prototype.toString.call(obj) === '[object Object]';
+}

appveyor.yml

@@ -8,7 +8,6 @@ init:
 environment:
   MOCHA_REPORTER: "mocha-appveyor-reporter"
   matrix:
-    - nodejs_version: "8"
     - nodejs_version: "10"
 
 # Install scripts. (runs after repo cloning)

package.json

@@ -92,7 +92,7 @@
     "**/engine.io": "~3.3.0"
   },
   "engines": {
-    "node": "8.* || >= 10"
+    "node": ">= 10"
   },
   "publishConfig": {
     "registry": "https://registry.npmjs.org/"