或 ||
let a = 0 || 1
a -> 1
let a = 1 || 0
a -> 1
let a = 1 || 2
a -> 1
let a = 2 || 1
a -> 2
let a = 0 || null
a -> null
let a = null || undefined
a -> undefined
一真一假返回真,两真返回第一个,两假返回后面那个。
与 &&
let b = 0 && 1
b -> 0
let b = 1 && 2
b -> 2
let b = 2 && 1
b -> 1
let b = null && undefined
b -> null
一真一假返回假,两真返回后面那个,两假返回第一个。
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