exercise.js

/**
 * Prompt:
 *
 * A customer has reported a bug in one of our APIs. The `/applicants` endpoint
 * is designed to respond to search queries for applicants according to query
 * parameters that are sent along with the request.
 *
 * For example, this request:
 *    GET /applicants?resume=1
 *
 * Should return all applicants that have submitted a resume.
 *
 * This request:
 *   GET /applicants?country=USA&background_check=1
 *
 * Should return all applicants from the USA that have passed a background check.
 *
 *
 * However, the customer has reported that in response to this request:
 *  GET /applicants?resume=1&background_check=1&country=USA
 * 
 * They seem to be getting back all USA applicants that have submitted a resume,
 * whether or not they've actually passed a background check.
 *
 * After confirming that the problem is reproducible, we've narrowed down the
 * problem to the controller that responds to `GET /applicants` requests below.
 *
 * We'll pair together on diagnosing the problem and seeing if we can fix the
 * bug. Feel free to use any resources or reference materials you like, and feel
 * free to ask me questions.
 *
 * More important than actually finding/fixing the issue is that I want to
 * understand your thought process, so let me know what you're thinking and why
 * you're taking the steps you're taking.
 *
 * You can simulate the request that causes the bug by pressing the 'Run' button
 */

function getApplicants(params) {
  // load all applicants from database
	let applicants = APPLICANTS;

  // We need to treat background checks and resumes special because they exist in different systems
  if ('background_check' in params) {
    applicants = filterByBackgroundChecks(applicants, params['background_check']);
    delete params['background_check'];
  }
  
  if ('resume' in params) {
    applicants = filterByResume(applicants, params['resume']);
    delete params['resume'];
  }
  
  applicants = filterByParams(applicants, params);

  return applicants;
}


function filterByBackgroundChecks(applicants, shouldHavePassed) {
  // load background checks from external service
  const backgroundChecks = BACKGROUND_CHECKS;
  
	const checkPassedByName = {};
  for (const check of backgroundChecks) {
    checkPassedByName[check.name] = check.passed;
  }
  
  const filtered = [];
  for (const applicant of APPLICANTS) {
    if (checkPassedByName[applicant.name] === shouldHavePassed) {
      filtered.push(applicant);
    }
  }

  return filtered;
}


function filterByResume(applicants, shouldHaveSubmitted) {
  // load resumes from S3
  const resumes = RESUMES;
  
  const resumeSubmittedByName = {};
  for (const resume of resumes) {
    resumeSubmittedByName[resume.name] = resume.submitted;
  }

  const filtered = [];
  for (const applicant of APPLICANTS) {
    if (resumeSubmittedByName[applicant.name] === shouldHaveSubmitted) {
      filtered.push(applicant);
    }
  }

  return filtered;
}

function filterByParams(applicants, params) {
  const filtered = [];

  for (const applicant of applicants) {
    let match = true;
    for (const param in params) {
      match = match && applicant[param] === params[param];

      if(!match) {
        break;
      }
    }

    if(match) {
      filtered.push(applicant);
    }
  }

  return filtered;
}

const APPLICANTS = [
  {
    name: 'Dan Raloff',
    country: 'USA',
    phone: '15555555555',
  },
  {
    name: 'Spam Sawzall',
    country: 'USA',
    phone: '15555555555',
  },
  {
    name: 'Sherm Wermbly',
    country: 'USA',
    phone: '15555555555',
  },
  {
    name: 'Cat Dancin',
    country: 'USA',
    phone: '15555555555',
  },
  {
    name: 'Danny Schmanny',
    country: 'España',
    phone: '15555555555',
  },
  {
    name: 'Richy Rich',
    country: 'Switzerland',
    phone: '1$$$$$$$$$$'
  },
];

const BACKGROUND_CHECKS = [
  { name: 'Dan Raloff'    , passed: 1 },
  { name: 'Spam Sawzall'  , passed: 0 },
  { name: 'Sherm Wermbly' , passed: 1 },
  { name: 'Cat Dancin'    , passed: 0 },
  { name: 'Danny Schmanny', passed: 0 },
  { name: 'Richy Rich'    , passed: 1 }
];

const RESUMES = [
  { name: 'Dan Raloff'    , submitted: 1 },
  { name: 'Spam Sawzall'  , submitted: 1 },
  { name: 'Sherm Wermbly' , submitted: 1 },
  { name: 'Cat Dancin'    , submitted: 0 },
  { name: 'Danny Schmanny', submitted: 1 },
  { name: 'Richy Rich'    , submitted: 0 }
];

console.log(
  JSON.stringify(
    getApplicants({
      country: 'USA',
      resume: 1,
      background_check: 1
    }),
  null,
  2
));