JavaScript type casting

Question

Consider empty JavaScript array:

var a = [];
alert(a == false); // shows true
alert(!a); // shows false!

How to explain this? What are the

Answer 1

When comparing an object to a primitive value via the == operator, the object coerces into an primitive value itself (number or string). In this case [] coerces into 0, then false coerces into 0:

[] == false
0 == false
0 == 0

which is true.

The ! operator coerces into boolean and then inverts the value. [] into boolean is true (like with any object). Then invert to become false

![]
!true
false