因为：false、0、null、 NaN、'' 为 false其他均为true 推论：typeof [] == 'object' && [] !== null 所以：Boolean([]) = true 所以：!Boolean([]) = false[] == ![] [] == false Number([]) == 0 0 == false => trueECMA-262 The comparison x == y, where x and y are values, produces true or false. Such a comparison is performed as follows: 1.If Type(x) is the same as Type(y), then a.If Type(x) is Undefined, return true. b.If Type(x) is Null, return true. c.If Type(x) is Number, then i.If x is NaN, return false. ii.If y is NaN, return false. iii.If x is the same Number value as y, return true. iv.If x is +0 and y is −0, return true. v.If x is −0 and y is +0, return true. vi.Return false. d.If Type(x) is String, then return true if x and y are exactly the same sequence of characters (same length and same characters in corresponding positions). Otherwise, return false. e.If Type(x) is Boolean, return true if x and y are both true or both false. Otherwise, return false. f.Return true if x and y refer to the same object. Otherwise, return false. 2.If x is null and y is undefined, return true. 3.If x is undefined and y is null, return true. 4.If Type(x) is Number and Type(y) is String, return the result of the comparison x == ToNumber(y). 5.If Type(x) is String and Type(y) is Number, return the result of the comparison ToNumber(x) == y. 6.If Type(x) is Boolean, return the result of the comparison ToNumber(x) == y. 7.If Type(y) is Boolean, return the result of the comparison x == ToNumber(y). 8.If Type(x) is either String or Number and Type(y) is Object, return the result of the comparison x == ToPrimitive(y).
推论：typeof [] == 'object' && [] !== null
所以：Boolean([]) = true
所以：!Boolean([]) = false[] == ![]
[] == false
Number([]) == 0
0 == false => trueECMA-262
The comparison x == y, where x and y are values, produces true or false. Such a comparison is performed as follows:
1.If Type(x) is the same as Type(y), then
a.If Type(x) is Undefined, return true.
b.If Type(x) is Null, return true.
c.If Type(x) is Number, then
i.If x is NaN, return false.
ii.If y is NaN, return false.
iii.If x is the same Number value as y, return true.
iv.If x is +0 and y is −0, return true.
v.If x is −0 and y is +0, return true.
vi.Return false.
d.If Type(x) is String, then return true if x and y are exactly the same sequence of characters (same length and same characters in corresponding positions). Otherwise, return false.
e.If Type(x) is Boolean, return true if x and y are both true or both false. Otherwise, return false.
f.Return true if x and y refer to the same object. Otherwise, return false.
2.If x is null and y is undefined, return true.
3.If x is undefined and y is null, return true.
4.If Type(x) is Number and Type(y) is String, return the result of the comparison x == ToNumber(y).
5.If Type(x) is String and Type(y) is Number, return the result of the comparison ToNumber(x) == y.
6.If Type(x) is Boolean, return the result of the comparison ToNumber(x) == y.
7.If Type(y) is Boolean, return the result of the comparison x == ToNumber(y).
8.If Type(x) is either String or Number and Type(y) is Object, return the result of the comparison x == ToPrimitive(y).
true[]==![]输出ture或者false?false