[JavaScript] Algorithms and Data Structures Projects

These are my notes while doing the course JavaScript Algorithms and Data Structures on https://www.freecodecamp.org. I highly recommend it if you prefer to try things directly rather than watching videos.

1. Palindrome Checker

function palindrome(str) {

  // clear string
  str = str.toLowerCase().replace(/[^a-z0-9]/g, "");

  // reverse string
  let strBack = str.split("").reverse().join("");

  // palindrome?
  return (str === strBack) ? true : false;

}

palindrome("_eye");
palindrome("five|\_/|four");
palindrome("1 eye for of 1 eye.");

2. Roman Numeral Converter

function convertToRoman(num) {

  const lookup = {M:1000,CM:900,D:500,CD:400,C:100,XC:90,L:50,XL:40,X:10,IX:9,V:5,IV:4,I:1};
  let roman = '';

  for ( let i in lookup ) {
    while ( num >= lookup[i] ) {
      roman += i;
      num -= lookup[i];
    }
  }
  return roman;
}

convertToRoman(6);

3. Caesars Cipher

function rot13(str) {

  const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  const length = alphabet.length;
  let decode = "";

  const getROT13 = index => {
    return (index+13 >= length) ? alphabet[13-(length-index)] : alphabet[index+13];
  }

  for (let i=0; i<str.length; i++) {

    let index = alphabet.indexOf(str[i]);

    decode += (index<0) ? str[i] : getROT13(index); 

  }

  return decode;
}

rot13("SERR PBQR PNZC")
rot13("SERR CVMMN!")

4. Telephone Number Validator

function telephoneCheck(str) {

  let regexCheck = /^(1.*){0,1}(\d{3}|[(]\d{3}[)])[\s|-]*\d{3}.*\d{4}$/g; 

  let result = regexCheck.test(str);

  if (result) {
    let length = str.match(/\d/g).length;
    result = (length == 7 || length == 10 || (length == 11 && str[0] == 1)) ? true : false;
  }

  console.log(str.match(regexCheck));
  console.log(result);

  return result;

}


telephoneCheck("555-555-5555");
telephoneCheck("1 555-555-5555");
telephoneCheck("1 (555) 555-5555");
telephoneCheck("5555555555");
telephoneCheck("555-555-5555")
telephoneCheck("(555)555-5555")
telephoneCheck("1(555)555-5555")
telephoneCheck("1 555)555-5555") //false
telephoneCheck("(6054756961)")  //false
telephoneCheck("2 (757) 622-7382") //false
telephoneCheck("10 (757) 622-7382") //false

5. Cash Register

function checkCashRegister(price, cash, cid) {

  let changeArr = [];

  const currency = { "ONE HUNDRED": 100, "TWENTY": 20, "TEN": 10, "FIVE": 5, "ONE": 1, "QUARTER": 0.25, "DIME": 0.1, "NICKEL": 0.05, "PENNY": 0.01 }

  const substract = (a, b) => parseFloat(a - b).toPrecision(4);

  const calcAmount = (change, curr) => {
                let rest = change % curr;
                let div = substract(change, rest) / curr;    
                return div * curr;
  }

  let change = substract(cash, price);

  //check if cid equals to change
  //or if cid is already not enough
  let sum = 0;
  for (let k=0; k<cid.length;k++) {
    sum += cid[k][1]
  }
  if (sum == change) {
    return {status: "CLOSED", change: cid};
  } else if (sum < change) {
    return {status: "INSUFFICIENT_FUNDS", change: []};
  }

  //calculate change
  for (let i in currency) {
    if (change > currency[i]) {    
      for (let j=0; j<cid.length;j++) {
        if (i == cid[j][0]) {
          let amount = cid[j][1];
          if (substract(change, amount) < 0)  {
            amount = calcAmount(change, currency[i]);
          }
          change = substract(change, amount);
          changeArr.push([i, amount]);
        }
      }
    } 
  }

  if (change != 0) {
    //not able to give the correct change
    return {status: "INSUFFICIENT_FUNDS", change: []};
  }
  return {status: "OPEN", change: changeArr};
}

checkCashRegister(19.5, 20, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]);

checkCashRegister(3.26, 100, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]])

checkCashRegister(19.5, 20, [["PENNY", 0.01], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]])

checkCashRegister(19.5, 20, [["PENNY", 0.01], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 1], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]])

checkCashRegister(19.5, 20, [["PENNY", 0.5], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]])