Push

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题目

在类型系统里实现通用的 Array.push 。

例如：

type Result = Push<[1, 2], "3">; // [1, 2, '3']

解答

type Push<T extends unknown[], U> = [...T, ...[U]]

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why use unknow insteadof any

see: https://www.typescriptlang.org/docs/handbook/2/functions.html#unknown

The unknown type represents any value. This is similar to the any type, but is safer because it’s not legal to do anything with an unknown value: