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Javascriptで配列内に特定の要素が存在するかどうかの判定

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JSの配列にはexistsとかcontainsなどとかいうメソッドは無いがindexOfを利用して以下のように判定できる。

var arr = ["a", "b", "c"];

if (arr.indexOf("a") >= 0){
  // 存在する
}

if (arr.indexOf("a") == -1){
  // 存在しない
}

参考

Javascriptで配列にある値が存在するかどうかを確認する方法について - 主にプログラムを勉強するブログ
http://d.hatena.ne.jp/artgear/20130124/javascript_array_contain_how_to

koyopro
フリーのエンジニアでスマホアプリ開発がメイン。 最近はKaggleで遊んだりしてる。
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