React + Typescript documentation

prerequisities - TypeScript, React Fundamentals

1. Introduction to TypeScript

What is TypeScript?
- programming language developed by microsoft
- superset of JavaScript
Why TypeScript?
- adds static typing to JavaScript
- it helps to see bugs when writing codes; easy to find and fix bugs
- gives auto suggestion
- provides better documentation
Course outcomes
- props types
  - built-in data type props
  - user defined data type props
  - events props
- hooks types

2. Environment setup

install node & VSCode
install react+ts -> npx create-react-app appName --template typescript

3. typescript for Props - built in types

built in types example -> string, number, boolean
extension .ts and component extension is .tsx not .js or .jsx

// auto completion -> props.
// if we pass anything other than string as name props we will get error
// component props is an object
// User.tsx (version-1)
import React from "react";
const User = (props: {
  name: string;
  email: string;
  age: number;
  isRegistered: boolean;
}) => {
  return (
    <div style={{ border: "1px solid", margin: "1rem" }}>
      <h2>{props.name}</h2>
      <p>{props.email}</p>
      <p>{props.age} years old</p>
      {props.isRegistered ? (
        <p>Registered Student</p>
      ) : (
        <p>Unregistered Student</p>
      )}
    </div>
  );
};

export default User;

// User.tsx (version-2)
import React from "react";

type UserProps = {
  name: string;
  email: string;
  age: number;
  isRegistered: boolean;
};
const User = (props: UserProps) => {
  return (
    <div style={{ border: "1px solid", margin: "1rem" }}>
      <h2>{props.name}</h2>
      <p>{props.email}</p>
      <p>{props.age} years old</p>
      {props.isRegistered ? (
        <p>Registered Student</p>
      ) : (
        <p>Unregistered Student</p>
      )}
    </div>
  );
};
export default User;

// User.tsx (version-3)
import React from "react";
type UserProps = {
  name: string;
  email: string;
  age: number;
  isRegistered: boolean;
};
const User = ({ name, email, age, isRegistered }: UserProps) => {
  return (
    <div style={{ border: "1px solid", margin: "1rem" }}>
      <h2>{name}</h2>
      <p>{email}</p>
      <p>{age} years old</p>
      {isRegistered ? <p>Registered Student</p> : <p>Unregistered Student</p>}
    </div>
  );
};
export default User;

// App.tsx
import React from "react";
import "./App.css";
import User from "./components/User";

function App() {
  return (
    <div className="App">
      <h1>User Management App</h1>
      <User
        name="anisul islam"
        email="anisul2010s@yahoo.co.uk"
        age={32}
        isRegistered={true}
      />
      <User
        name="Rabeya Begum"
        email="rabu2010s@yahoo.co.uk"
        age={31}
        isRegistered={false}
      />
    </div>
  );
}

export default App;

// void
const handleClick = (): void => {
  console.log("clicked");
};

4. typescript for Props - User defined types

Object, Array, Union, enum, tuple, any, custom type

object props

import React from "react";

type UserProps = {
  user: {
    name: string;
    email: string;
    age: number;
    isRegistered: boolean;
  };
};
const User = ({ user }: UserProps) => {
  return (
    <div style={{ border: "1px solid", margin: "1rem" }}>
      <h2>{user.name}</h2>
      <p>{user.email}</p>
      <p>{user.age} years old</p>
      {user.isRegistered ? (
        <p>Registered Student</p>
      ) : (
        <p>Unregistered Student</p>
      )}
    </div>
  );
};

export default User;

// App.tsx
import React from "react";
import "./App.css";
import User from "./components/User";

const user1 = {
  name: "anisul islam",
  email: "anisul2010s@yahoo.co.uk",
  age: 32,
  isRegistered: true,
};
const user2 = {
  name: "Rabeya Begum",
  email: "rabu2010s@yahoo.co.uk",
  age: 31,
  isRegistered: false,
};

function App() {
  return (
    <div className="App">
      <h1>User Management App</h1>
      <User user={user1} />
      <User user={user2} />
    </div>
  );
}

export default App;

// more updates for App.tsx
import React from "react";
import "./App.css";
import User from "./components/User";

const users = [
  {
    id: 1,
    name: "anisul islam",
    email: "anisul2010s@yahoo.co.uk",
    age: 32,
    isRegistered: true,
  },
  {
    id: 2,
    name: "Rabeya Begum",
    email: "rabu2010s@yahoo.co.uk",
    age: 31,
    isRegistered: false,
  },
];

function App() {
  return (
    <div className="App">
      <h1>User Management App</h1>
      {users.map((user) => (
        <User key={user.id} user={user} />
      ))}
    </div>
  );
}

export default App;

array props

// simple example
import React from "react";

type UserProps = {
  lang: string[];
};
const User = ({ lang }: UserProps) => {
  return (
    <div style={{ border: "1px solid", margin: "1rem" }}>
      <p>
        Speaks:{" "}
        {lang.map((language, index) => {
          return <span key={index}>{language} </span>;
        })}
      </p>
    </div>
  );
};
export default User;

// App.tsx
import React from "react";
import "./App.css";
import User from "./components/User";
function App() {
  return (
    <div className="App">
      <h1>User Management App</h1>
      <User lang={["Bangla", "English", "Finnish"]} />
    </div>
  );
}
export default App;

// complex example
import React from "react";

type UserProps = {
  user: {
    name: string;
    email: string;
    age: number;
    isRegistered: boolean;
    languages: string[];
  };
};
const User = ({ user }: UserProps) => {
  return (
    <div style={{ border: "1px solid", margin: "1rem" }}>
      <h2>{user.name}</h2>
      <p>{user.email}</p>
      <p>{user.age} years old</p>
      {user.isRegistered ? (
        <p>Registered Student</p>
      ) : (
        <p>Unregistered Student</p>
      )}
      <p>
        Speaks:{" "}
        {user.languages.map((language, index) => {
          return <span key={index}>{language} </span>;
        })}
      </p>
    </div>
  );
};
export default User;

// App.tsx
import React from "react";
import "./App.css";
import User from "./components/User";

const users = [
  {
    id: 1,
    name: "anisul islam",
    email: "anisul2010s@yahoo.co.uk",
    age: 32,
    isRegistered: true,
    languages: ["Bangla", "English"],
  },
  {
    id: 2,
    name: "Rabeya Begum",
    email: "rabu2010s@yahoo.co.uk",
    age: 31,
    isRegistered: false,
    languages: ["Bangla", "English", "Finnish"],
  },
];

function App() {
  return (
    <div className="App">
      <h1>User Management App</h1>
      {users.map((user) => (
        <User key={user.id} user={user} />
      ))}
    </div>
  );
}
export default App;

// one more array example

// App.tsx
import React from "react";
import "./App.css";
import User from "./components/User";
const users = [
  {
    id: 1,
    name: "anisul islam",
    email: "anisul2010s@yahoo.co.uk",
  },
  {
    id: 2,
    name: "Rabeya Begum",
    email: "rabu2010s@yahoo.co.uk",
  },
];

function App() {
  return (
    <div className="App">
      <h1>User Management App</h1>
      <User users={users} />
    </div>
  );
}
export default App;

// User.tsx
import React from "react";
type UserProps = {
  users: {
    id: number;
    name: string;
    email: string;
  }[];
};
const User = ({ users }: UserProps) => {
  return (
    <div>
      {users.map((user) => {
        const { id, name, email } = user;
        return (
          <div key={id} style={{ border: "1px solid", margin: "1rem" }}>
            <p>{name}</p>
            <p>{email}</p>
          </div>
        );
      })}
    </div>
  );
};
export default User;

union of types

// Message.tsx
import React from "react";

type MessageProps = {
  text: "ADD" | "UPDATE" | "DELETE";
};

const Message = (props: MessageProps) => {
  if (props.text === "ADD") {
    return <p>User is added</p>;
  } else if (props.text === "UPDATE") {
    return <p>User is updated</p>;
  }
  return <p>User is deleted</p>;
};

export default Message;

// App.tsx
function App() {
  return (
    <div className="App">
      <h1>User Management App</h1>
      <Message text="UPDATE" />
      {/* <User users={users} /> */}
    </div>
  );
}

export default App;

children props

// Card.tsx
import React from "react";
type CardProps = {
  children: React.ReactNode;
};
const Card = (props: CardProps) => {
  return <div className="card">{props.children}</div>;
};

export default Card;

//User.tsx
import React from "react";
import Card from "./Card";

type UserProps = {
  user: {
    name: string;
    email: string;
    age: number;
    isRegistered: boolean;
    languages: string[];
  };
};
const User = ({ user }: UserProps) => {
  return (
    <Card>
      <h2>{user.name}</h2>
      <p>{user.email}</p>
      <p>{user.age} years old</p>
      {user.isRegistered ? (
        <p>Registered Student</p>
      ) : (
        <p>Unregistered Student</p>
      )}
      <p>
        Speaks:{" "}
        {user.languages.map((language, index) => {
          return <span key={index}>{language} </span>;
        })}
      </p>
    </Card>
  );
};
export default User;

5. Typing Event Props

example

    // Typing event props
  click event: event: React.MouseEvent<HTMLButtonElement>
  type ButtonProps = {
  handleClick: (event: React.MouseEvent<HTMLButtonElement>) => void;
  handleChange: (event: React.ChangeEvent<HTMLInputElement>) => void
  };

  //App.tsx
  import React, { useState } from "react";

  type NewUserProps = {
    name: string;
    email: string;
  };
  const NewUser = () => {
    const [user, setUser] = useState<NewUserProps>({ name: "", email: "" });

    const handleChange = (event: React.ChangeEvent<HTMLInputElement>) => {
      const fieldName = event.target.name;
      setUser({ ...user, [fieldName]: event.target.value });
    };

    const handleSubmit = (event: React.FormEvent<HTMLFormElement>) => {
      event.preventDefault();
      console.log(user);
    };
    return (
      <div>
        <h2>Create User</h2>
        <form onSubmit={handleSubmit}>
          <div>
            <label htmlFor="name">
              Name
              <input
                type="text"
                id="name"
                name="name"
                value={user.name}
                onChange={handleChange}
                required
              />
            </label>
          </div>
          <div>
            <label htmlFor="email">
              Email
              <input
                type="email"
                id="email"
                name="email"
                value={user.email}
                onChange={handleChange}
                required
              />
            </label>
          </div>
          <button type="submit">Create User</button>
        </form>
      </div>
      );
    };

    export default NewUser;

6. Style Props

example

// props for styles -> React.CSSProperties
import React from "react";

type ButtonProps = {
  styles: React.CSSProperties;
};

const Button = (props: ButtonProps) => {
  return <button style={props.styles}>click me</button>;
};

export default Button;

import "./App.css";
import Button from "./components/Button";

function App() {
  return (
    <div className="App">
      <Button
        styles={{ backgroundColor: "green", padding: "1rem", color: "white" }}
      />
    </div>
  );
}

export default App;

7. Typing useState Hooks

example

import React, { useState } from "react";
import "./App.css";

const App = () => {
  // type is automatically infereed as number
  const [count, setCount] = useState(0);

  const handleIncrement = (): void => {
    setCount((count) => count + 1);
  };

  const handleDecrement = (): void => {
    setCount((count) => count - 1);
  };

  return (
    <div className="App">
      <h1>Count : {count}</h1>
      <button onClick={handleIncrement}>+</button>
      <button onClick={handleDecrement}>-</button>
    </div>
  );
};

export default App;

// dealing with future values in useState Hook
import React, { useState } from "react";
import "./App.css";

type User = {
  id: number;
  name: string;
};

const App = () => {
  // const [data, setData] = useState<null | string>(null);
  const [data, setData] = useState<null | User>(null);

  const handleSetData = () => {
    // setData("Anisul islam");
    setData({ id: 101, name: "anisul islam" });
    console.log(data);
  };

  return (
    <div className="App">
      <h1>UseState Future value</h1>
      <button onClick={handleSetData}>set data</button>
      {/* {data && <p>{data}</p>} */}
    <!-- <p>{data?.id}</p> -->
    <!-- <p>{data?.name}</p> -->
    </div>
  );
};

export default App;

// type asertion - without optional chaining operator
import React, { useState } from "react";
import "./App.css";

type User = {
  id: number;
  name: string;
};

const App = () => {
  // const [data, setData] = useState<null | string>(null);
  const [data, setData] = useState<User>({} as User);

  const handleSetData = () => {
    // setData("Anisul islam");
    setData({ id: 101, name: "anisul islam" });
    console.log(data);
  };

  return (
    <div className="App">
      <h1>UseState Future value</h1>
      <button onClick={handleSetData}>set data</button>
      {/* {data && <p>{data}</p>} */}
      <p>{data.id}</p>
      <p>{data.name}</p>
    </div>
  );
};

export default App;

8. Typing useReducer Hooks

example

// Counter.tsx
import React, { useReducer } from "react";

const INCREMENT = "INCREMENT";
const INCREMENTBYAMOUNT = "INCREMENTBYAMOUNT";
const RESET = "RESET";
const DECREMENT = "DECREMENT";

const initialState = { count: 0 };
type counterState = {
  count: number;
};

type IncrementActionType = { type: typeof INCREMENT };
type IncrementByAmountActionType = {
  type: typeof INCREMENTBYAMOUNT;
  payload: number;
};
type ResetActionType = { type: typeof RESET };
type DecrementActionType = { type: typeof DECREMENT };

type counterActionType =
  | IncrementActionType
  | DecrementActionType
  | ResetActionType
  | IncrementByAmountActionType;

const reducer = (state: counterState, action: counterActionType) => {
  switch (action.type) {
    case INCREMENT:
      return { count: state.count + 1 };
    case INCREMENTBYAMOUNT:
      return { count: state.count + action.payload };
    case RESET:
      return { count: 0 };
    case DECREMENT:
      return { count: state.count - 1 };
    default:
      throw new Error();
  }
};

const Counter = () => {
  const [state, dispatch] = useReducer(reducer, initialState);
  return (
    <div>
      <h1> Count : {state.count}</h1>
      <button
        onClick={() => {
          dispatch({ type: INCREMENT });
        }}
      >
        Increment
      </button>
      <button
        onClick={() => {
          dispatch({ type: INCREMENTBYAMOUNT, payload: 5 });
        }}
      >
        IncrementByAmount
      </button>
      <button
        onClick={() => {
          dispatch({ type: RESET });
        }}
      >
        Reset
      </button>
      <button
        onClick={() => {
          dispatch({ type: DECREMENT });
        }}
      >
        Decrement
      </button>
    </div>
  );
};

export default Counter;

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React + Typescript documentation

1. Introduction to TypeScript

2. Environment setup

3. typescript for Props - built in types

4. typescript for Props - User defined types

5. Typing Event Props

6. Style Props

7. Typing useState Hooks

8. Typing useReducer Hooks

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React + Typescript documentation

1. Introduction to TypeScript

2. Environment setup

3. typescript for Props - built in types

4. typescript for Props - User defined types

5. Typing Event Props

6. Style Props

7. Typing useState Hooks

8. Typing useReducer Hooks

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