js truthy 和 falsy 究竟是什么truthy 即当数据类型自动转换（或隐式转换）为 Boolean 类型为

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In JavaScript, a truthy value is a value that is considered true when encountered in a Boolean context. All values are truthy unless they are defined as falsy. That is, all values are truthy except false, 0, -0, 0n, "", null, undefined, and NaN.

JavaScript uses type coercion in Boolean contexts. truthy 即当数据类型自动转换（或隐式转换）为 Boolean 类型为 true 的值。truthy值比较多，所以可以这样记，除了值是 falsy，其他都是 truthy。值为 falsy 的有 false, 0, -0, 0n, "", null, undefined, and NaN

truthy values 例子

if (true)
if ({})
if ([])
if (42)
if ("0")
if ("false")
if (new Date())
if (-42)
if (12n)
if (3.14)
if (-3.14)
if (Infinity)
if (-Infinity)

falsy values 例子

if (false)
if (null)
if (undefined)
if (0)
if (-0)
if (0n)
if (NaN)
if ("")

所有 falsy values 解释

Value	Description
`false`	The keyword `false`.
`0`	The `Number` zero (so, also `0.0`, etc., and `0x0`).
`-0`	The `Number` negative zero (so, also `-0.0`, etc., and `-0x0`).
`0n`	The `BigInt` zero (so, also `0x0n`). Note that there is no `BigInt` negative zero — the negation of `0n` is `0n`.
`""`, `''`, ``	Empty string value.
null	null — the absence of any value.
undefined	undefined — the primitive value.
NaN	NaN — not a number.
`document.all`	Objects are falsy if and only if they have the [[IsHTMLDDA]] internal slot.That slot only exists in `document.all` and cannot be set using JavaScript.