Iterable - JavaScript Challenges

You can find all the code in this post in the repo Github.

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Iterable related challenges

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Iterable

Rewriting the Symbol.iterator properity to create an iterator object.

The iterator object includes two properties:

1. value: the current value of the current iteration call, undefined when the iterator is over.
2. done: whether the iteration has finished.

/**
 * @param {any} data
 * @return {object}
 */

function createCustomIterable(data) {
  return {
    [Symbol.iterator]() {
      let index = 0;
      return {
        next() {
          if (index < data.length) {
            return {
              value: data[index++],
              done: false,
            };
          } else {
            return {
              value: undefined,
              done: true,
            };
          }
        },
      };
    },
  };
}

// Usage example:
const customIterable = createCustomIterable([1, 2, 3, 4]);

// Using for...of loop
for (const item of customIterable) {
  console.log(item);
}
/**
 * 1
 * 2
 * 3
 * 4
 */

// Using spread operator
const arrayFromIterable = [...customIterable];
console.log(arrayFromIterable); // => [1, 2, 3, 4]

// Using Array.from()
const anotherArray = Array.from(customIterable);
console.log(anotherArray); // => [1, 2, 3, 4]

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Reference

• Iterator - MDN
• Iteration protocols - MDN
• [Iterator.prototypeSymbol.iterator - MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Iterator/Symbol.iterator)