for...of

const array1 = ["a", "b", "c"];

for (const element of array1) {
  console.log(element);
}

// Expected output: "a"
// Expected output: "b"
// Expected output: "c"

for (variable of iterable) {
  statement;
}

let iterable = [10, 20, 30];

for (let value of iterable) {
  console.log(value);
}
// 10
// 20
// 30

let iterable = [10, 20, 30];

for (const value of iterable) {
  console.log(value);
}
// 10
// 20
// 30

let iterable = "boo";

for (let value of iterable) {
  console.log(value);
}
// "b"
// "o"
// "o"

let iterable = new Uint8Array([0x00, 0xff]);

for (let value of iterable) {
  console.log(value);
}
// 0
// 255

let iterable = new Map([
  ["a", 1],
  ["b", 2],
  ["c", 3],
]);

for (let entry of iterable) {
  console.log(entry);
}
// [a, 1]
// [b, 2]
// [c, 3]

for (let [key, value] of iterable) {
  console.log(value);
}
// 1
// 2
// 3

let iterable = new Set([1, 1, 2, 2, 3, 3]);

for (let value of iterable) {
  console.log(value);
}
// 1
// 2
// 3

// :  NodeList.prototype[Symbol.iterator]
//   
let articleParagraphs = document.querySelectorAll("article > p");

for (let paragraph of articleParagraphs) {
  paragraph.classList.add("read");
}

function* fibonacci() {
  //  
  let [prev, curr] = [1, 1];
  while (true) {
    [prev, curr] = [curr, prev + curr];
    yield curr;
  }
}

for (let n of fibonacci()) {
  console.log(n);
  // 1000  
  if (n >= 1000) {
    break;
  }
}

var iterable = {
  [Symbol.iterator]() {
    return {
      i: 0,
      next() {
        if (this.i < 3) {
          return { value: this.i++, done: false };
        }
        return { value: undefined, done: true };
      },
    };
  },
};

for (var value of iterable) {
  console.log(value);
}
// 0
// 1
// 2

Object.prototype.objCustom = function () {};
Array.prototype.arrCustom = function () {};

let iterable = [3, 5, 7];
iterable.foo = "hello";

for (let i in iterable) {
  console.log(i); // logs 0, 1, 2, "foo", "arrCustom", "objCustom"
}

for (let i of iterable) {
  console.log(i); // logs 3, 5, 7
}