一行检查属性是否存在并有条件地设置它？

Question

I would like to rewrite this code in one line, if at all possible:

//Obj is my mystery object - I don't know whether or not property x exists, but if it does, I want to set it!

if (Obj.x) {
   Obj.x = (Obj.x > 0) ? Obj.x++ : Obj.x--;
}

Answer 1

One possible way:

Obj.x && (Obj.x = Obj.x > 0 ? Obj.x++ : Obj.x--);

Or less ideal:

Obj.x = Obj.x ? Obj.x > 0 ? Obj.x++ : Obj.x-- : Obj.x;

FWIW , your case is a bit strange, as you do the post increment (and decrement), which amends the value, but immediately save the initial value back to the variable, so the value doesn't change. You'd better either not save the value back:

Obj.x && (Obj.x > 0 ? Obj.x++ : Obj.x--);

or do it differently:

Obj.x && (Obj.x = Obj.x > 0 ? Obj.x + 1 : Obj.x - 1);