ID Generator

idGenerator.js

function* idGenerator(prefix = "", initialIndex = 0) {
  let index = initialIndex;
  while (true) yield `${prefix}${index++}`;
}

idGenerator.test.js

describe("idGenerator", () => {
  it("should generate user ids", () => {
    const userIds = idGenerator("USER_");
    for (let idx = 0; idx < 42; idx++) {
      userIds.next();
    }
    expect(userIds.next().value).toEqual("USER_42");
  });

  it("should generate post ids", () => {
    const postIds = idGenerator("POST_", 1000);
    for (let idx = 0; idx < 111; idx++) {
      postIds.next();
    }
    expect(postIds.next().value).toEqual("POST_1111");
  });
});