how can an arbitrary object be configured to work in a for....of loop code example

Example 1: for in and for of in js

const iterable = [10, 20, 30];

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

Example 2: es6 for-of loop

for (let itme of list) {
  ...
}