Wraps an Array with generator functions.

aarray.js

const it = function(a) {
  return new Aarray(a2g(a));
};
      
const a2g = function*(a) {
  for (let v of a) {
    yield v;
  }
};

const Aarray = function(g) {
  this.g = g;
};

Aarray.prototype.map = function(f) {
  const og = this.g;
  this.g = (function*() {
    for (let v of og) {
      yield f(v);
    }
  }());
  return this;
};

Aarray.prototype.filter = function(f) {
  const og = this.g;
  this.g = (function*() {
    for (let v of og) {
      if (f(v)) yield v;
    }
  }());
  return this;
};

Aarray.prototype[Symbol.iterator] = function*() {
  yield* this.g;
};

Aarray.prototype.find = function(f) {
  for (let v of this.g) {
    if (f(v)) return v;
  }
};

/*

// Example:

const a = new Array(1e9);  // Huge array
a[0] = '4'
a[1] = '42';
it(a).map(e => parseInt(e)).filter(e => e % 4).find(e => e%2 == 0);

*/