for...in loop

The for…in loop iterates over the enumerable property names (keys) of an object. It is commonly used to traverse object properties, but it can also iterate over array indices.

const person = {
  name: "John",
  age: 30,
  city: "New York",
};

for (let key in person) {
  console.log(key + ": " + person[key]);
}
// Output: name: John, age: 30, city: New York

// With arrays (iterates over indices)
const colors = ["red", "green", "blue"];
for (let index in colors) {
  console.log(index + ": " + colors[index]);
}
// Output: 0: red, 1: green, 2: blue