/* xhr.js */
class XHR {
 get(url) {
 return new Promise((resolve, reject) => {
 const xhr = new XMLHttpRequest();
 xhr.onreadystatechange = () => {
 if (xhr.readyState === 4) {
 if (xhr.status >= 200 && (xhr.status < 300 || xhr.status === 304)) {
 if (xhr.responseText) {
 resolve(JSON.parse(xhr.responseText));
 } else {
 resolve(xhr.responseText);
 }
 } else {
 reject(`XHR unsuccessful:${xhr.status}`);
 }
 }
 };
 xhr.open('get', url, true);
 xhr.setRequestHeader('content-type', 'application/json');
 xhr.send(null);
 });
 }

 post(url, data) {
 return new Promise((resolve, reject) => {
 const xhr = new XMLHttpRequest();
 xhr.onreadystatechange = () => {
 if (xhr.readyState === 4) {
 if (xhr.status >= 200 && (xhr.status < 300 || xhr.status === 304)) {
 resolve(JSON.parse(xhr.responseText));
 } else {
 reject(`XHR unsuccessful:${xhr.status}`);
 }
 }
 };
 xhr.open('post', url, true);
 xhr.setRequestHeader('content-type', 'application/json');
 xhr.send(JSON.stringify(data));
 });
 }
}

/* Vue插件要求提供install方法：https://cn.vuejs.org/v2/guide/plugins.html */
XHR.install = (Vue) => {
 Vue.prototype.$get = new XHR().get;
 Vue.prototype.$post = new XHR().post;
};

export default XHR;

const Foo = resolve => {
 /* require.ensure 是 Webpack 的特殊語法，用來設置 code-split point
 （代碼分塊）*/
 require.ensure(['./Foo.vue'], () => {
 resolve(require('./Foo.vue'))
 })
}
/* 另一種寫法 */
const Foo = resolve => require(['./Foo.vue'], resolve);

const router = new VueRouter({
 routes: [
 { path: '/foo', component: Foo }
 ]
})