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HTML

              
                <p>一応、DOMの増減はjQueryでもできる。<br>
しかしこのサンプルの設計だと、増やした後の状態を取得しづらい。<br>
つまり、今何個Blockがあるのか、等をチェックするのが難しい。<br>
つまり、状態の管理が難しい。状態の管理が難しいと、いつかアプリケーションが破綻する。</p>
<p>なぜ状態の管理が難しいかというと、状態がすべて本物のDOMとして管理されているので、<br>それを捜査・取得する必要があるから。</p>
<p>⇨だとすれば、状態をJSで管理して、その状態をjQueryで反映させれば良い。</p>

<button class="add">Add</button>
<button class="delete">Delete</button>
<div class="wrapper">
	<div class="block"></div>
</div>

              
            
!

CSS

              
                p
	margin : 10px

.block
	float: left
	width: 100px
	height: 100px
	box-sizing: border-box
	border: 1px solid black
	background-color: blue

.add
	display: block
	width: 100px
	height: 50px

.delete
	display: block
	width: 100px
	height: 50px
	
              
            
!

JS

              
                $('.add').on('click', () => {
	$('.wrapper').append('<div class="block"></div>');
});

$('.delete').on('click', () => {
	$('.block:last').remove();
});


              
            
!
999px

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