import export

import React, { Component } from 'react';

表示React是default导出的，Component是命名导出的。

如何导出类

单文件导出1

// Module.js
class ModuleA {}
class ModuleB {}
export default ModuleA;
export { ModuleB };
// demo.js
import ModuleA, { ModuleB } from './Module';

单文件导出2

// Module.js
class ModuleA {}
class ModuleB {}
class Module {}
Module.A = ModuleA;
Module.B = ModuleB;
export default Module;
// demo.js
import Module from './Module';
const {A, B} = Module;

多文件导出1

// CoreModule.js
export { default as EventManager } from './EventManager';
export { default as AccountManager } from './AccountManager';
// demo.js
import { EventManager, AccountManager } from './CoreModule';

多文件导出2

// CoreModule.js
import AccountManager from './AccountManager';
import EventManager from './EventManager';
export { EventManager, AccountManager }
// demo.js
import { EventManager, AccountManager } from './CoreModule';

单例

import EventEmitter from 'EventEmitter';
class EventManager {
    static sInstance = null;
    constructor() {
        this._eventEmitter = new EventEmitter();
    }

    addListener(eventName, callback) {
        if (typeof callback !== 'function') {
            throw new TypeError('listener argument must be a function');
        }
        this._eventEmitter.addListener(eventName, callback);
    }

    removeListener(eventName, callback) {
        if (typeof callback !== 'function') {
            throw new TypeError('listener argument must be a function');
        }
        this._eventEmitter.removeListener(eventName, callback);
    }

    removeAllListeners() {
        this._eventEmitter.removeAllListeners();
    }

    triggerEvent(eventName, ...args) {
        this._eventEmitter.emit(eventName, args);
    }

    static getInstance() {
        if (!EventManager.sInstance) {
            EventManager.sInstance = new EventManager();
        }
        return EventManager.sInstance;
    }
}
EventManager.EventAccount = "account";
export default EventManager;