1//Form (Parent)
2import React, { useState, Component } from 'react';
3import Input from '../../shared/input-box/InputBox'
4
5const Form = function (props) {
6
7    const [value, setValue] = useState('');
8
9    const onchange = (data) => {
10        setValue(data)
11        console.log("Form>", data);
12    }
13
14    return (
15        <div>
16            <Input data={value} onchange={(e) => { onchange(e) }}/>
17        </div>
18    );
19}
20export default Form;
21
22//Input Box (Child)
23import React from 'react';
24
25const Input = function (props) {
26    console.log("Props in Input :", props);
27
28    const handleChange = event => {
29        props.onchange(event.target.value);
30    }
31
32    return (
33        <div>
34            <input placeholder="name"
35                id="name"
36                onChange= {handleChange}
37            />
38        </div>
39    );
40}
41export default Input;

1const { useState } = React;
2
3function PageComponent() {
4  const [count, setCount] = useState(0);
5  const increment = () => {
6    setCount(count + 1)
7  }
8
9  return (
10    <div className="App">
11      <ChildComponent onClick={increment} count={count} />         
12      <h2>count {count}</h2>
13      (count should be updated from child)
14    </div>
15  );
16}
17
18const ChildComponent = ({ onClick, count }) => {
19  return (
20    <button onClick={onClick}>
21       Click me {count}
22    </button>
23  )
24};
25
26ReactDOM.render(<PageComponent />, document.getElementById("root"));

1Parent:
2
3<div className="col-sm-9">
4     <SelectLanguage onSelectLanguage={this.handleLanguage} /> 
5</div>
6
7Child:
8
9handleLangChange = () => {
10    var lang = this.dropdown.value;
11    this.props.onSelectLanguage(lang);            
12}

1import React, { useState } from 'react';
2import './App.css';
3import Todo from './components/Todo'
4
5
6
7function App() {
8    const [todos, setTodos] = useState([
9        {
10          id: 1,
11          title: 'This is first list'
12        },
13        {
14          id: 2,
15          title: 'This is second list'
16        },
17        {
18          id: 3,
19          title: 'This is third list'
20        },
21    ]);
22
23return (
24        <div className="App">
25            <h1></h1>
26            <Todo todos={todos}/> //This is how i'm passing props in parent component
27        </div>
28    );
29}
30
31export default App;
32
33
34function Todo(props) {
35    return (
36        <div>
37            {props.todos.map(todo => { // using props in child component and looping
38                return (
39                    <h1>{todo.title}</h1>
40                )
41            })}
42        </div>  
43    );
44}