Record<K, V> in TypeScript: Type-Safe Key-Value Objects

Record is a utility type in TypeScript that allows creating a new object type with specific keys and values. It provides a convenient way to define a type for objects where keys can be limited to specific values, and values have a certain type.

Syntax:

Record<K, T>

• K — type of object keys (e.g., strings or numbers).
• T — type of values corresponding to these keys.

The Record type allows defining that an object must have a certain set of keys and values, making it very useful when working with predefined keys and value types.

Record Usage Example

• Creating an object with predictable keys and values:

  Suppose we have a list of roles in an application, and we want to create an object where each key (role) corresponds to an array of strings representing user permissions.

  type UserRoles = "admin" | "user" | "guest";
  type RolePermissions = Record<UserRoles, string[]>;
  
  const rolePermissions: RolePermissions = {
    admin: ["create", "edit", "delete"],
    user: ["view", "edit"],
    guest: ["view"],
  };
  

  • UserRoles is a type representing user roles (e.g., "admin", "user", "guest").
  • Record<UserRoles, string[]> creates an object where keys are strings corresponding to roles, and values are arrays of strings containing access permissions for each role.

• Using Record to create objects with dynamic keys: You can use Record to create objects with dynamic keys, for example, based on enum values.

  enum Status {
    Active = "active",
    Inactive = "inactive",
    Pending = "pending",
  }
  
  type StatusMessage = Record<Status, string>;
  
  const statusMessages: StatusMessage = {
    [Status.Active]: "Your account is active.",
    [Status.Inactive]: "Your account is inactive.",
    [Status.Pending]: "Your account is pending approval.",
  };
  

  • Status is an enum representing possible statuses.
  • Record<Status, string> creates an object where keys are values from the Status enum, and values are strings representing messages for each status.