英文:
How do i compare a [null] list?
问题
我有一个列表,返回[null]
,但我想用[]
替换它
我正在使用useEffect()
,但我真的找不到一个与null
比较时返回true的表达式。
我尝试过:
listToCompare === null // false
listToCompare[0] === null // false
listToCompare === undefined // false
listToCompare === [null] // error even before compiling
这很烦人,因为[null]
返回.length
为1
,而我需要它为0。
有人能帮我找到一个与[null]比较时返回true的表达式吗?
真的很困惑一个[null]
列表到底是什么:(
英文:
I have a list which is returning [null]
but I want to replace that with []
I'm using useEffect()
but I'm literally not able to find an expression that returns true when compared with null
.
I've tried:
listToCompare === null // false
listToCompare[0] === null // false
listToCompare === undefined // false
listToCompare === [null] // error even before compiling
This is irritating because [null]
returns .length
as 1
when I need it to be 0.
Can someone help me find an expression to return true when compared to [null]
Really confused on what a [null]
list even is
答案1
得分: 0
以下是您要翻译的内容:
const listToCompare = [null];
const isNull = !listToCompare.filter(Boolean).length
console.log(isNull) // 返回 true
英文:
You could try
const listToCompare = [null];
const isNull = !listToCompare.filter(Boolean).length
console.log(isNull) // returns true
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