JavaScript Algorithms and Node.js Online Test

Consider the following package.json for a Node.js application:

{
  "name": "skill-measure-app",
  "private": true,
  "version": "1.0.0",
  "main": "lib/main.js",
  "scripts": {
    "build": "npm run cleanup & npm run test & npm run publish",
    "cleanup": "rm -fr ./lib",
    "test": "jest",
    "publish": "npm publish lib"
  },
  "dependencies": {
     "jest": "^23.0.1",
     "custom-package": "file:../custom-package"
  }
}

Select all the correct statements.

(Select all acceptable answers.)

Implement the ensure function so that it throws an error if called without arguments or the argument is undefined. Otherwise it should return the given value.

A playlist is considered a repeating playlist if any of the songs contain a reference to a previous song in the playlist. Otherwise, the playlist will end with the last song which points to undefined.

Implement the method isRepeatingPlaylist that, efficiently with respect to time used, returns true if a playlist is repeating or false if it is not.

For example, the following code prints "true" as both songs point to each other.

let first = new Song("Hello");
let second = new Song("Eye of the tiger");

first.nextSong = second;
second.nextSong = first;

console.log(first.isRepeatingPlaylist());