Comment by cookiengineer

Technically you could just use an assignment ternary expression for this:

    const y = (x === true) ? true : false;

I used this kind of style for argument initialization when I was writing JS code, right at the top of my function bodies, due to ES not being able to specify real nullable default values. (and I'm setting apart why I think undefined as a value is pointless legacy).

    Composite.prototype.SetPosition(x, y, z) {

        x = (isNumber(x) && x >= 0 && x <= 1337) ? x : null;
        y = (isNumber(y) && y >= 0 && y <= 1337) ? y : null;
        z = isNumber(z) ? z : null;

        if x !== null && y !== null && z !== null {
            // use clamped values
        }

    }