App.js

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

const App = () => {
  const [todos, setTodos] = useState([]);

  const toggleComplete = i =>
    setTodos(todos.map(
      (todo, k) =>
        k === i
          ? {
              ...todo,
              complete: !todo.complete,
            }
          : todo
    ));

  return (
    <div className="App">
      <Form
        onSubmit={inputText =>
          setTodos([{ inputText, complete: false }, ...todos])
        }
      />
      <div>
        {todos &&
          todos.map(({ inputText, complete}, i) => (
            <div 
            key={inputText} 
            onClick={() => toggleComplete(i)}
            style={{ 
              textDecoration: complete ? "line-through" : "", 
              color: complete ? "red" : "black", 
            }}>
              {inputText}
            </div>
          ))}
      </div>
    </div>
  );
};

export default App;

Form.jsx

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

const useInputValue = initialValue => {
  const [value, setValue] = useState(initialValue);

  return {
    value,
    onChange: e => setValue(e.target.value),
    resetValue: () => setValue(""),
  };
};

const Form = ({ onSubmit }) => {
  const {resetValue, ...inputText} = useInputValue("");

  return (
    <form
      onSubmit={e => {
        e.preventDefault();
        onSubmit(inputText.value);
        resetValue()
      }}
    >
      <input {...inputText} />
    </form>
  );
};

export default Form;

package.json

{
  "name": "todo",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "react": "^16.7.0-alpha.0",
    "react-dom": "^16.7.0-alpha.0",
    "react-scripts": "2.0.5"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": [
    ">0.2%",
    "not dead",
    "not ie <= 11",
    "not op_mini all"
  ]
}