copy-constructor.js

class Point {
  constructor(...args) {
    switch (args.length) {
      case 2: {
        // Normal constructor
        const [x, y] = args;
        this.x = x;
        this.y = y;
        break;
      }
      case 1: {
        // Copy constructor
        const [other] = args;
        this.x = other.x;
        this.y = other.y;
        break;
      }
      default:
        throw new Error();
    }
  }
}

both are valid and you could even provide both

The static variant has the advantage that it plays nice with other scenarios:

const foo = Point.fromOther(otherPoint) ;// aka copy
const foo = Point.fromLineStart(line); // conversion
const foo = Point.fromMidpoint([...geometries]);
...