yield test

yield.test.js

const slice = Array.prototype.slice;

const isGenerator = (obj) => {
  return 'function' == typeof obj.next && 'function' == typeof obj.throw;
}

function isPromise(obj = {}) {
  return 'function' == typeof obj.then;
}

function toPromise(obj) {
  if (isPromise(obj)) {
    return obj;
  } else {
    return Promise.resolve(obj);
  }
}

function co(gen) {
  let ctx = this;
  let args = slice.call(arguments, 1);
  let ret;

  return new Promise((resolve, reject) => {
    if (typeof gen === 'function') {
      gen = gen.apply(ctx, args);
    }
    if (!gen || typeof gen.next !== 'function') {
      return gen;
    }

    function next(ret) {
      if (ret.done) return resolve(ret.value);
      toPromise(ret.value).then(value => {
        next(gen.next(value));
      }).catch(error => {
        reject(error);
      });
    }

    next(gen.next());
  })
}

co(function* (val) {
  let a = yield Promise.resolve(val);
  let b = yield Promise.resolve(val + 1);
  return a + b;
}, 3).then(r => {
  console.log(r, '============ co ==============');
});


console.log('------------------- increment -----------------');

function* inc() {
  var g = 0;
  while (true) {
    g += 1;
    yield g;
  }
}

const iterator = inc();
const a = iterator.next().value
console.log(a);
console.log(iterator.next(a).value);

console.log('------------------- fibonacci ------------------');

function* fib() {
  var a = 1;
  var b = 1;
  var tmp;
  while(true) {
    yield a;
    tmp = b;
    b = a + b;
    a = tmp;
  }
}

const fibGen = fib();
console.log(fibGen.next().value);
console.log(fibGen.next().value);
console.log(fibGen.next().value);
console.log(fibGen.next().value);
console.log(fibGen.next().value);
console.log(fibGen.next().value);