javascript - 为什么 localStorage 返回大小写为 null 且未定义的字符串值

Question

当我保存null/undefined时值进入localStorage 。我使用 localStorage.getItem 时收到的结果将是一个字符串 ( "null" or "undefined" )

localStorage.setItem("item1", null)
localStorage.setItem("item2", undefined)

const item1 = localStorage.getItem("item1")
const item2 = localStorage.getItem("item2")

console.log(item1) // The result will be "null" not null
console.log(item2) // The result will be "undefined" not undefined

谁能帮我解释一下这个案例!

Answer 1

Js 将其字符串化到本地存储

storage.setItem(keyName, keyValue)

keyName and KeyValue both are of type DOMString

DOMString is a UTF-16 string. As JavaScript already uses such strings, DOMString is mapped directly to a String.

Passing null to a method or parameter accepting a DOMString typically stringifies to "null"

我看到我们同时有 2 个答案，所以只需添加他的部分 mdn docs和 DOMString