Just another math stuff:

let a = 0;

a += !(a[a]/a[a]==a[a]/a[a]) // a = 1

Explanation

  • We are trying to use number as an array. Nothing good will happen this way.
  • a[a] will return undefined and a[a]/a[a] will return NaN (it is definitely not a number!)
  • Comparing NaN with NaN will return false and after inversion it will be true. After that — we add 1 to variable.