parametricGeometry not working

I used This code

function math(u,v){
let x=u+v,
return new THREE.Vector3(x,y.z)
var normalGeom = new THREE.ParametricGeometry(math,64,64)
var normalMat = new THREE.MeshBasicMaterial({color: 0xff0000 });
var normal = new THREE.Mesh(normalGeom, normalMat);

got this

The math() function needs the third parameter of THREE.Vector3.

The docs mention THREE.ParametricGeometries.klein in the code snippet, which you can find here and see how it works and what it does: three.js/ParametricGeometries.js at 58c2f5a8f41e2d709c1af03583bc80b827486c9a · mrdoob/three.js · GitHub

Thank you sir it worked