var arr = [1,2,3];

for (let i = 0; i < arr.length; i++) {
  console.log(`${arr[i]} is at index ${i}`);
}

// 1 is at index 0.
// 2 is at index 1.
// 3 is at index 2.

var str = 'Woof';

for (let i = 0; i < arr.length; i++) {
  console.log(`${str[i]} is at index ${i}.`);
}

// W is at index 0.
// o is at index 1.
// o is at index 2.
// f is at index 3.

var str = 'hello world';

str.split(' ').forEach(function(element, index) {
  console.log(`${arr[i]} is at index ${i}`);
});

// hello is at index 0.
// world is at index 1.

var arr = [1,2,3];
for (let val of arr) {
  console.log(`The value is ${val}`);
}

// The value is 1
// The value is 2
// The value is 3

var str = 'OOP';
for (let char of str) {
  console.log(`The letter is "${char}".`);
}

// The letter is "O".
// The letter is "O".
// The letter is "P".

var obj = { day1: "Matt", day2: "Elie", day3: "Joel", day4: "Michael" };

for (let key in obj) {
  console.log(`${obj[key]} teaches on ${key}.`);
}

// Matt teaches on day1.
// Elie teaches on day2.
// Joel teaches on day3.
// Michael teaches on day4.

function isPalindrome(str) {
    let left = 0;
    let right = str.length - 1;
    
    while (left < right) {
      if (str[left] !== str[right]) {
        return false;
      }
      left++;
      right--;
    }
    
    return true;
}