JaysonChiang

const DropDownList = () => {
  const [focus, setFocus] = useState(false);
  const ref = useRef(null);

  useEffect(() => {
    const listener = (event) => {
      if ( ref.current && event.target && ref.current.contains(event.target)) {
        return;
      }
     

JaysonChiang

import axios, { AxiosError, AxiosResponse } from 'axios';
import token from './somewhere';

interface Todo {
  id: string;
  title: string;
}

interface User {
  id: string;

JaysonChiang

import axios from 'axios';
import { token } from './somewhere';

axios.defaults.baseURL = 'https://jsonplaceholder.typicode.com';

axios.interceptors.request.use((config) => {
  if (token) {
    config.headers.Authorization = `Bearer ${token}`;
  }
  return config;

JaysonChiang

import axios from 'axios';

axios.defaults.baseURL = 'https://jsonplaceholder.typicode.com';

axios.interceptors.response.use(res => res.data
, error => {
  const { data, status, config } = error.response;
  switch(status) {
    case 400:
      console.error(data);

JaysonChiang

import axios from 'axios';

axios.defaults.baseURL = 'https://jsonplaceholder.typicode.com';

const api = {
  getData: () => axios.get('/todos/1')
};

export default api;

JaysonChiang

const subject = {
  observers: [],
  subscribe(fn) {
    this.observers.push(fn)
  },
  notify(arg) {
    this.observers.forEach(fn => fn(arg));
  }
}

JaysonChiang

const subject = {
  observers: [],
  subscribe(observer) {
    this.observers.push(observer)
  },
  notify(message) {
    this.observers.forEach(observer => observer.update(message));
  }
}

JaysonChiang

const joe = {
  update(message) {
    console.log(`Joe receive ${message}`);
  }
}

const jason = {
  update(message) {
    console.log(`Jayson read ${message}`);
  }

JaysonChiang

import { useSelector } from './useSelector';

const TodoList: React.FC = () => {
  const { todos } = useSelector((state) => state.todos);

  return (
    <ul>
      {todos.map((todo) => (
        <li>{todo}</li>
      ))}

JaysonChiang

import { useSelector } from 'react-redux';

const TodoList: React.FC = () => {
  const { todos } = useSelector((state) => state.todos);
  // Property 'todos' does not exist on type 'DefaultRootState'.

  return (
    <ul>
      {todos.map((todo) => (
        <li>{todo}</li>