validation function for permissive inputs

validator.js

  //////////////////////////////
  //  Validate point & point-like objects
  //////////////////////////////
  static isPointLike(thing) {

    // RETURNS true if exactly what we want
    if (thing instanceof Point) return true;

    //////////////////////
    // RETURNS true if its kinda-like what we want, that is:
    //    has properties x,y oftype 'number' but not NaN numbers
    // RETURNS false if thing is neither a point nor point-like,
    //    or is empty string, undefined, NaN, null
    return !!thing
      && typeof thing.x === "number"
      && !isNaN(thing.x)
      && typeof thing.y === "number"
      && !isNaN(thing.y);
  }