型別（或資料型別）是能決定 value 該存為何種類型的特性：例如 JavaScript 的 Boolean 只能存為 true/false 兩者其一、而字串（String）能存為文字字串、Number 則能存城任何類型的數字……等等。
型別也能決定哪些操作是有效的：例如說整數（integer）可以與整數相乘，但不能與字串相乘。
深入了解
基本知識
- 維基百科的資料型別
- JavaScript 的資料型別
型別
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