javascript - Using the -- operator in a while loop produces unexpected results -

in formula,

var x = 5; while(x--) { console.log(x) } 

the output is

4 3 2 1 0 

why 0 output? on fifth iteration, x-- equal 0 falsey, loop should not run.

on same token, returns true

var x = 1; (x--) == true; 

but returns false

0 == true 

x-- evaluates first , decrements variable. if use --x instead, expect.