InputArea.jsx

import React, {useState, useEffect} from 'react';

export default () => {
    const [input, setInput] = useState([]);

    useEffect(() => {
        addInput();
    }, []);

    const addInput = () => {
      setInput([...input, renderInput()]);
    };

    const renderInput = () => {
        return (
          <div key={input.length + 1}>
              <input type="text" />
              <span><button onClick={addInput}>+</button></span>
          </div>
        );
    }

    console.log(input);

    return (
        <div>
            {input}
        </div>
    );
};