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Reactでfor文を使う

Last updated at Posted at 2020-11-28

#したかったこと
JSX内で表の列をfor文を用いることで、繰り返し処理する。
理由)デザインを変える時に、一つ一つ変更するのが面倒だった。

解決前のコード

<tr>
  <th style={{fontWeight: 'bold',fontSize:40}}>1set</th>
  <th><input style={{height:52, width:80,borderStyle:"none", borderRadius:4}}/><span style={{fontSize:40}}>kg</span></th>
  <th><input style={{height:52, width:70,borderStyle:"none", borderRadius:4}}/><span style={{fontSize:40}}></span></th>
</tr>
<tr>
  <th style={{fontWeight: 'bold',fontSize:40}}>2set</th>
  <th><input style={{height:52, width:80,borderStyle:"none", borderRadius:4}}/><span style={{fontSize:40}}>kg</span></th>
  <th><input style={{height:52, width:70,borderStyle:"none", borderRadius:4}}/><span style={{fontSize:40}}></span></th>
</tr>
<tr>
  <th style={{fontWeight: 'bold',fontSize:40}}>3set</th>
  <th><input style={{height:52, width:80,borderStyle:"none", borderRadius:4}}/><span style={{fontSize:40}}>kg</span></th>
  <th><input style={{height:52, width:70,borderStyle:"none", borderRadius:4}}/><span style={{fontSize:40}}></span></th>
</tr>

##解決策
・即時関数を使う。
・for文のループで出力された列を作成したリストにプッシュし、最後にリストを返す。(これをしないでfor文内で値を返すと、1ループ目で値を返してしまいました。)

解決後のコード
{(() =>{
  const item=[];
  for(let i=1; i <5; i++) {
    item.push(
    <tr>
      <th style={{fontWeight: 'bold',fontSize:40}}>{i}set</th>
      <th><input style={{height:52, width:80,borderStyle:"none", borderRadius:4}}/><span style={{fontSize:40}}>kg</span></th>
      <th><input style={{height:52, width:70,borderStyle:"none", borderRadius:4}}/><span style={{fontSize:40}}></span></th>
    </tr>
    )
  }
  return(item)
})()}

###結果
スクリーンショット 2020-11-28 17.44.47.png

参考にした記事 - Qiita

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