jQuery

예시

<p class="hello">안녕</p>
<script>
  $('.hello').html('바보'); 
</script>

<p class="hello">안녕</p>
<script>
  $('.hello').css('color', 'red');
</script>

<p class="hello">안녕</p>
<script>
  $('.hello').addClass('클래스명');
  $('.hello').removeClass('클래스명');
  $('.hello').toggleClass('클래스명');
</script>

<p class="hello">안녕</p>
<p class="hello">안녕</p>
<p class="hello">안녕</p>
<script>
  document.querySelectorAll('.hello')[0].innerHTML = '바보';
  document.querySelectorAll('.hello')[1].innerHTML = '바보';
  document.querySelectorAll('.hello')[2].innerHTML = '바보';
</script>

jQuery사용시

<p class="hello">안녕</p>
<p class="hello">안녕</p>
<p class="hello">안녕</p>
<script>
  $('.hello').html('바보');
</script>

<p class="hello">안녕</p>
<button class="test-btn">버튼</button>
<script>
  $('.test-btn').on('click', function(){
    어쩌구~
  });
</script>

<p class="hello">안녕</p>
<button class="test-btn">버튼</button>
<script>
  $('.test-btn').on('click', function(){
    $('.hello').fadeOut();
  });
</script>