Same here. VM that is incapable of producing the same code from 

    var x = this.x;
    var y = this.y;
    var z = this.z;
    return Math.sqrt(x*x + y*y + z*z);

and 

    return Math.sqrt(this.x*this.x + this.y*this.y + this.z*this.z);

is kinda lousy.