"use strict";
const nodemailer = require("nodemailer");

// async..await is not allowed in global scope, must use a wrapper
async function main() {
  // Generate test SMTP service account from ethereal.email
  // Only needed if you don't have a real mail account for testing
  let testAccount = await nodemailer.createTestAccount();

  // create reusable transporter object using the default SMTP transport
  let transporter = nodemailer.createTransport({
    host: "smtp.ethereal.email",
    port: 587,
    secure: false, // true for 465, false for other ports
    auth: {
      user: testAccount.user, // generated ethereal user
      pass: testAccount.pass, // generated ethereal password
    },
  });

  // send mail with defined transport object
  let info = await transporter.sendMail({
    from: '"Fred Foo 👻" <[email protected]>', // sender address
    to: "[email protected], [email protected]", // list of receivers
    subject: "Hello ✔", // Subject line
    text: "Hello world?", // plain text body
    html: "<b>Hello world?</b>", // html body
  });

  console.log("Message sent: %s", info.messageId);
  // Message sent: <[email protected]>

  // Preview only available when sending through an Ethereal account
  console.log("Preview URL: %s", nodemailer.getTestMessageUrl(info));
  // Preview URL: https://ethereal.email/message/WaQKMgKddxQDoou...
}

main().catch(console.error);

const permutations = arr => {
  if (arr.length <= 2) return arr.length === 2 ? [arr, [arr[1], arr[0]]] : arr;
  return arr.reduce(
    (acc, item, i) =>
      acc.concat(
        permutations([...arr.slice(0, i), ...arr.slice(i + 1)]).map(val => [
          item,
          ...val,
        ])
      ),
    []
  );
};
permutations([1, 33, 5]);
// [ [1, 33, 5], [1, 5, 33], [33, 1, 5], [33, 5, 1], [5, 1, 33], [5, 33, 1] ]

arr = [] // empty array
const isEmpty = arr => !Array.isArray(arr) || arr.length === 0;

// Examples
isEmpty([]); // true
isEmpty([1, 2, 3]); // false

const powerset = arr =>
  arr.reduce((a, v) => a.concat(a.map(r => r.concat(v))), [[]]);
  
powerset([1, 2]); // [[], [1], [2], [1, 2]]

let nums = [1,2,3,1]

var containsDuplicate = function(nums) {
    let obj = {};
    for(let i =0; i< nums.length; i++){
        if(obj[nums[i]]){
            obj[nums[i]] += 1;
            return true;
        }else{
            obj[nums[i]] = 1;
        }
    }
    return false;
};

console.log(containsDuplicate(nums));

const primes = num => {
  let arr = Array.from({ length: num - 1 }).map((x, i) => i + 2),
    sqroot = Math.floor(Math.sqrt(num)),
    numsTillSqroot = Array.from({ length: sqroot - 1 }).map((x, i) => i + 2);
  numsTillSqroot.forEach(x => (arr = arr.filter(y => y % x !== 0 || y === x)));
  return arr;
};

primes(10); // [2, 3, 5, 7]