为什么'in'关键字无法在数组中找到元素？

Question

Below is returning the true

a = 'status'
a=='status'

while below is returning false

a = 'status'
a in ['status'] --> False

If '==' is returning true then please let me know why 'in' is returning false ?

Answer 1

The in operator doesn't check if an array/collection contains an element. It checks if the object on the right has a property with the name of the value on the left.

// Both return 'true'.
'foo' in { foo: 100, bar: 200 }
'filter' in ['hello']

You probably want to use indexOf :

['status'].indexOf(a) >= 0

Or for newer versions of JavaScript, includes :

['status'].includes(a)