Full-Stack JavaScript

for..of loop

The for..of loops are used for looping through iterable objects such as arrays:

let arr = [10, 20, 30];

for (let item of arr) {
   console.log(item); 
}

It also works with strings:

const greeting = "Hello!"
for (const ch of greeting) { 
  console.log(ch);
}

for..in loop

The for..in loop allows you to iterate over keys of enumerable object properties.

const user = {
   firstName: "Ali",
   lastName: "Madooei"
};

for (const key in user) {
   console.log(key, user[key]);
}

It works with strings and arrays too, but iterates over the indices:

const arr = [10, 11, 12];
for (const key in arr) {
  // console.log(key);
  console.log(arr[key]);
}

const greeting = "Hello!"
for (const key in greeting) { 
  // console.log(key);
  console.log(greeting[key]);
}