Final answer:
The add operator method in the vector class can be implemented by creating a new vector object with the sum of the x, y, and z magnitudes of the two vectors being added.
Step-by-step explanation:
The implementation of the add operator method in the vector class can be done by creating a new vector object and setting its x, y, and z magnitudes using the sum of the corresponding magnitudes of the two vectors being added.
class Vector {
 constructor(x, y, z) {
 this.x = x;
 this.y = y;
 this.z = z;
 } 
 add(otherVector) {
 let newX = this.x + otherVector.x;
 let newY = this.y + otherVector.y;
 let newZ = this.z + otherVector.z; 
 return new Vector(newX, newY, newZ);
 }
}