How to get the coordinates

Questions
1

How to get the coordinates (? ,?, Z),when the mouse click the screen, the click point may be a blank area without any object

2

Maybe this thread might help you:

4 
export function transformCoordToThree(mouse, camera, renderer) {
    const ray = new THREE.Ray();
    const {domElement} = renderer;
    const threePoint = {
        x: (mouse.x / domElement.clientWidth) * 2 - 1,
        y: -(mouse.y / domElement.clientHeight) * 2 + 1
    };
    ray.origin.setFromMatrixPosition(camera.matrixWorld);
    ray.direction.set(threePoint.x, threePoint.y, 0.5).unproject(camera).sub(ray.origin).normalize();
    const plane = new THREE.Plane(new THREE.Vector3(0, 0, 1))
    return ray.intersectPlane(plane, new THREE.Vector3(0, 0, 0))
}

Thank you i get it