styled-componentsによるスタイル付け

Button.js

import styled from 'styled-components';

const Button = styled.button`
  font: inherit;
  padding: 0.5rem 1.5rem;
  border: 1px solid #8b005d;
  color: white;
  background: #8b005d;
  box-shadow: 0 0 4px rgba(0, 0, 0, 0.26);
  cursor: pointer;

  &:focus {
    outline: none;
  }

  &:hover,
  &:active {
    background: #ac0e77;
    border-color: #ac0e77;
    box-shadow: 0 0 8px rgba(0, 0, 0, 0.26);
  }
`;

export default Button;

CourseInput.js

import React, { useState } from 'react';
import styled from 'styled-components';
import Button from '../../UI/Button/Button';

const FormControl = styled.div`
  margin: 0.5rem 0;

  & label {
    font-weight: bold;
    display: block;
    margin-bottom: 0.5rem;
    color: ${(props) => (props.invalid ? 'red' : 'black')};
  }

  & input {
    display: block;
    width: 100%;
    border: 1px solid ${(props) => (props.invalid ? 'red' : '#ccc')};
    background: ${(props) => (props.invalid ? '#ffd7d7' : 'transparent')};
    font: inherit;
    line-height: 1.5rem;
    padding: 0 0.25rem;
  }

  & input:focus {
    outline: none;
    background: #fad0ec;
    border-color: #8b005d;
  }
`;

const CourseInput = (props) => {
  const [enteredValue, setEnteredValue] = useState('');
  const [isValid, setIsValid] = useState(true);

  const goalInputChangeHandler = (event) => {
    if (event.target.value.trim().length > 0) {
      setIsValid(true);
    }
    setEnteredValue(event.target.value);
  };

  const formSubmitHandler = (event) => {
    event.preventDefault();
    if (enteredValue.trim().length === 0) {
      setIsValid(false);
      return;
    }
    props.onAddGoal(enteredValue);
  };

  return (
    <form onSubmit={formSubmitHandler}>
      <FormControl invalid={!isValid}>
        <label>Course Goal</label>
        <input type='text' onChange={goalInputChangeHandler} />
      </FormControl>
      <Button type='submit'>Add Goal</Button>
    </form>
  );
};

export default CourseInput;