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Intersections of Types

An intersection type combines multiple types into one with the & operator. The resulting intersection type satisfies all the component types simultaneously.

type IndividualContributor = {
  id: number;
  name: string;
  tasks: string[];
};

type Manager = {
  directReports: number[];
};

type GoodManager = IndividualContributor & Manager;

const hunter: GoodManager = {
  id: 1,
  name: "Hunter Backmann",
  tasks: ["Fixing Lane's B*llsh*t code", "Vibe Coding"],
  directReports: [2, 3, 4],
};

A GoodManager must have all the properties of both an IndividualContributor and a Manager. When you intersect object types, TypeScript merges their properties:

type Point2D = {
  x: number;
  y: number;
};

type Point3D = Point2D & {
  z: number;
};

// Equivalent to:
// type Point3D = {
//   x: number;
//   y: number;
//   z: number;
// };

Assignment

Create and export new TextBot and VoiceBot types. They should each intersect with the existing SupportBot type but have the following additional properties:

TextBot:
- messageLog - an array of strings
- sendMessage - a function that takes a message string and returns a string
VoiceBot
- callLog - an array of strings
- phoneNumber - a string
- dialNumber - a function that takes a phoneNumber string and returns a string