Id generator in TypeScript

id_generator.ts

export function generateId(length: number): string {
    let outString: string = '';
    const inOptions: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';

    for (let i = 0; i < length; i++) {
        outString += inOptions.charAt(Math.floor(Math.random() * inOptions.length));
    }

    return outString;
}

export function generateFirestoreId(): string {
    return generateId(20);
}

id_generator_test.ts

import { expect } from "chai";
import { describe, it } from "mocha";
import {
  generateFirestoreId,
  generateId,
} from "../../../src/core/utils/id_generator";

describe("generateId()", () => {
  it("should generate an id with the given length", () => {
    const id = generateId(25);
    expect(id.length).is.equal(25);
  });
});

describe("generateFirestoreId()", () => {
  it("should generate an id with a length of 20", () => {
    const id = generateFirestoreId();
    expect(id.length).is.equal(20);
  });
});