Function createBuilder

Creates a factory function for building objects of a given type. Commonly used to create test objects for use in specs.

interface Message {
  id: number;
  text: string;
}

interface Options {
  cypherDistance: number;
}

declare function shiftCharacters(text: string, distance: number): string;

const buildMessage = createBuilder<Message, Options>(
  (seq) => ({ id: seq, text: `message ${seq}` }),
  (message, _seq, options) => {
    message.text = shiftCharacters(message.text, options.cypherDistance || 0);
  },
);

buildMessage(); // { id: 1, text: "message 1" }
buildMessage({ text: "Hello world!" }); // { id: 2, text: "Hello world!" }
buildMessage({ text: "abc" }, { cypherDistance: 3 }); // { id: 3, text: "def" }
Copy