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const bobs = ['bob', 'Bob', 'BOB', 'boB'] as const
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type Bob = typeof bobs[number]
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const isBobKindOf = (thing: string): boolean => bobs.includes(thing as Bob)
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const isBob = (thing: string): thing is Bob => bobs.includes(thing as Bob)
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const people = ['bob', 'smith', 'boB', 'smITH']
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const bobPeople = people.filter(isBobKindOf)
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const bobPeople2 = people.filter(isBob)
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const isKindOfFirstBob = people.find(isBobKindOf)
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const firstBob = people.find(isBob)
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const first = people[0]
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if (isBob(first)) {
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  console.log(first)
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} else {
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  console.log(first, 'not bob')
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}