JSFiddle - React, Tailwind, and code Playground

by jun68ykt

HTML

<script src="https://getfirebug.com/firebug-lite-debug.js"></script>

JavaScript

// 配列の中に特定の値が含まれているかの判定に includes を使う
const datas = ['hoge', 'fuga', 'piyo'];

console.log(datas.includes('fuga')); // => true
console.log(datas.includes('foo')); // => false

// includes では、NaNが含まれるかの判定が可能
const numbers = [1, 2, 3, NaN];

console.log(numbers.includes(NaN)); // => true
console.log(numbers.indexOf(NaN)); // => -1