1import React, { useState } from 'react';
2
3function Example() {
4  // Declare a new state variable, which we'll call "count"  
5  const [count, setCount] = useState(0);
6  return (
7    <div>
8      <p>You clicked {count} times</p>
9      <button onClick={() => setCount(count + 1)}>
10        Click me
11      </button>
12    </div>
13  );
14}

1class NameForm extends React.Component {
2  constructor(props) {
3    super(props);
4    this.state = {value: ''};
5    this.handleChange = this.handleChange.bind(this);
6    this.handleSubmit = this.handleSubmit.bind(this);
7  }
8
9  handleChange(event) {    this.setState({value: event.target.value});  }
10  handleSubmit(event) {
11    alert('A name was submitted: ' + this.state.value);
12    event.preventDefault();
13  }
14
15  render() {
16    return (
17      <form onSubmit={this.handleSubmit}>
18        <label>
19          Name:
20          <input type="text" value={this.state.value} onChange={this.handleChange} />        </label>
21        <input type="submit" value="Submit" />
22      </form>
23    );
24  }
25}

1const [count, setCount] = React.useState(0);
2  const [count2, setCount2] = React.useState(0);
3
4  // increments count by 1 when first button clicked
5  function handleClick(){
6    setCount(count + 1);
7  } 
8
9  // increments count2 by 1 when second button clicked
10  function handleClick2(){
11    setCount2(count2 + 1);
12  } 
13
14  return (
15    <div>
16      <h2>A React counter made with the useState Hook!</h2>
17      <p>You clicked {count} times</p>
18      <p>You clicked {count2} times</p>
19      <button onClick={handleClick}>
20        Click me
21      </button> 
22      <button onClick={handleClick2}>
23        Click me2
24      </button>
25  );

1import React, { useEffect } from 'react';
2
3export const App: React.FC = () => {
4  
5  useEffect(() => {
6        
7  }, [/*Here can enter some value to call again the content inside useEffect*/])
8  
9  return (
10    <div>Use Effect!</div>
11  );
12}

1class Example extends React.Component {
2  constructor(props) {
3    super(props);
4    this.state = {
5      count: 0
6    };
7  }
8
9  render() {
10    return (
11      <div>
12        <p>You clicked {this.state.count} times</p>
13        <button onClick={() => this.setState({ count: this.state.count + 1 })}>
14          Click me
15        </button>
16      </div>
17    );
18  }
19}

1import React, { useState } from 'react';
2
3function Example() {
4	
5  const [count, setCount] = useState(0);
6  
7  return (
8    <div>
9      <p>You clicked {count} times</p>
10      <button onClick={() => setCount(count + 1)}>
11        Click me
12      </button>
13    </div>
14  );
15}