What will this code return and why?

Question

function addOne (x) {

x--;
var y = x++;
var z = ++y;
return z - y;

}

addOne(5);

Answer 1

Where did you see this, in challenge I suppose? it's funny the code does a totally different job given the name : )

It returns zero by the way, I assume you already know pre and post increment/decrement, let's review that;

function addOne(x){
x--;
// x is still 5 x will decrement on the next instruction line.

var y = x++;
// here x becomes 4, and is still 4 when it is assigned to y, so y is 4 too.

var z = ++y;
// here y is incremented and becomes 5 before assigned to z, so z gets 5 too.

return z - y;
// both z & y is 5, so this is 5-5, equals zero.
}

FYI you can use Code Playground to test a code : )

Hth, cmiiw