For Of Iterables

Use for...of with a custom iterable.

for_of_iterable.js

const stop = 3;
const values = [];

const range = {
  [Symbol.iterator]() {
    let current = 1;
    return {
      next() {
        if (current <= stop) {
          const value = current;
          current = current + 1;
          return { value, done: false };
        }
        return { value: undefined, done: true };
      },
    };
  },
};

for (const value of range) {
  values.push(value * 10);
}

console.log("stop=" + stop);
console.log("scaled=" + values.join("-"));

for-of-iterable `for...of` reads from any object that provides `Symbol.iterator`. The loop keeps asking for the next value until the iterator is done.