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Overriding Built in Iterables

Below, a closure is used to pass the value of i to the iterator.


var s = new String('hello');   // = “hello" will allow auto-boxing
s[Symbol.iterator] = function() {   // always, [Symbol.iterator]() takes 0 argument
  return {   // the method must return an iterator
    next: function() {   // again, next() takes 0 argument
      if (this.i < 2) {
        this.i++;
        return { value: "abc"[this.i], done: false };
      } else {
        return { done: true };
      }
    },
    i: -1
  };
}

for (v of s) console.log(v);
console.log([...s]);

a b c ["a","b","c"]