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const ninjas = new Set(['kuma', 'hattori', 'yagyu']);
const samurai = new Set(['hattori', 'oda', 'tomoe']);

// 交集
const ninjaSamurais = new Set(
    [...ninjas].filter(ninja => {
        console.log(samurai.has(ninja), [...ninjas])
        return samurai.has(ninja) && ninja
    })
)
console.log(ninjaSamurais)

console.log(
    [...ninjas].filter(ninja => {
        console.log(samurai.has(ninja), [...ninjas])
        return samurai.has(ninja) && ninja
    })
)

console.log(1, 
   new Set(['hattori'])
)

// 差集
const pureNinjas = new Set(
    [...ninjas].filter(ninja => !samurai.has(ninja))
)
console.log(pureNinjas, [...ninjas].filter(ninja => !samurai.has(ninja)))

console.log(new Set(["kuma","yagyu"]), 2)
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