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[] == ![] 输出什么？ #1

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sihai00 opened this issue Jul 18, 2019 · 0 comments

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sihai00 commented Jul 18, 2019 •

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注意点1：逻辑非

!对象：false
!空字符串：true
!非空字符串：false
!数值0：true
!任务非0数值（包括Infinity）：false
!null：true
!NaN：true
!undefined：true

注意点2：隐式转换

如果有布尔值，将其转换为数值
如果有字符串和数值，将字符串转换为数值
如果有对象，先调用valueOf比较，如果还是对象或者数组，调用toString

[] == ![]

// !比==的优先级高，先执行!
[] == false

// 当比较中有布尔值时，优先把布尔值转化为数值
[] == 0

// 当比较中是对象，另一个是数值或字符串，把对象转换成基础类型的值再比较(valueOf 和 toString)
'' == 0

// 当字符串和数值对比时，把字符串转为数值进行对比
0 == 0         

// 结果：true

sihai00 added the javascript label

sihai00 self-assigned this

sihai00 added bug and removed bug labels

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