HardParts Promises and Iterators

iterators.js

// Type JavaScript here and click "Run Code" or press Ctrl + s
console.log('Hello, world!');

// CHALLENGE 1

function sumFunc(arr) {
  // YOUR CODE HERE
  let accumulator = 0;
	for (let i = 0; i < arr.length; i++) {
    accumulator += arr[i];
  }
  return accumulator;
}

// Uncomment the lines below to test your work
const array = [1, 2, 3, 4];
console.log('Challenge 1A', sumFunc(array)); // -> should log 10

function returnIterator(arr) {
  // YOUR CODE HERE
  let index = 0;
  return function() {
    const value = arr[index];
    index++;
    return value;
  }

}

// Uncomment the lines below to test your work
const array2 = ['a', 'b', 'c', 'd'];
const myIterator = returnIterator(array2);
console.log('Challenge 1B', myIterator()); // -> should log 'a'
console.log(myIterator()); // -> should log 'b'
console.log(myIterator()); // -> should log 'c'
console.log(myIterator()); // -> should log 'd'



// CHALLENGE 2

function nextIterator(arr) {
  // YOUR CODE HERE
	let index = 0;
  const iterator = {
    next: function () {
      const value = arr[index];
      index++;
      return value;
    }
  }
  return iterator;
}

// Uncomment the lines below to test your work
const array3 = [1, 2, 3];
const iteratorWithNext = nextIterator(array3);
console.log('Challenge 2', iteratorWithNext.next()); // -> should log 1
console.log(iteratorWithNext.next()); // -> should log 2
console.log(iteratorWithNext.next()); // -> should log 3



// CHALLENGE 3

function sumArray(arr) {
  // YOUR CODE HERE
  // use your nextIterator function
  let accumulator = 0;
  let iterator = nextIterator(arr);
  let next = iterator.next();
  while(next) {
    accumulator += next;
    next = iterator.next();
  }
	return accumulator
}

// Uncomment the lines below to test your work
const array4 = [1, 2, 3, 4];
console.log('Challenge 3', sumArray(array4)); // -> should log 10



// CHALLENGE 4

function setIterator(set) {
  // YOUR CODE HERE
  let setIterator = set.values();
  const iterator = {
    next: function () {
      var next = setIterator.next();
      return next['value'];
    }
  }
  return iterator;
}

// Uncomment the lines below to test your work
const mySet = new Set('hey');
const iterateSet = setIterator(mySet);
console.log('Challenge 4', iterateSet.next()); // -> should log 'h'
console.log(iterateSet.next()); // -> should log 'e'
console.log(iterateSet.next()); // -> should log 'y'



// CHALLENGE 5

function indexIterator(arr) {
  // YOUR CODE HERE
	let index = 0;
  const iterator = {
    next: function () {
      const value = arr[index];
      index++;
      return [index - 1, value];
    }
  }
  return iterator;
}

// Uncomment the lines below to test your work
const array5 = ['a', 'b', 'c', 'd'];
const iteratorWithIndex = indexIterator(array5);
console.log('Challenge 5', iteratorWithIndex.next()); // -> should log [0, 'a']
console.log(iteratorWithIndex.next()); // -> should log [1, 'b']
console.log(iteratorWithIndex.next()); // -> should log [2, 'c']



// CHALLENGE 6

function Words(string) {
  this.str = string;
}

Words.prototype[Symbol.iterator] = function() {
  // YOUR CODE HERE
  let index = 0;
  const splitStr = this.str.split(/\s/);
	return {
    next: function () {
      if (index < splitStr.length) {
        const value = splitStr[index];
        index ++;
        return {value: value, done: false};
      } else {
        return { done: true };
      }
    }
  }
}

// Uncomment the lines below to test your work
const helloWorld = new Words('Hello World');
for (let word of helloWorld) { console.log('Challenge 6', word); } // -> should log 'Hello' and 'World'

// CHALLENGE 7

function valueAndPrevIndex(array){
  let index = 0;
	return {
    sentence: function() {
      index++;
      let indexName = index;
      if (index - 1 === 0) {
        indexName = "first";
      }
      return "" + array[index - 1] + " was found after index " + indexName;
    }
  }
}

const returnedSentence = valueAndPrevIndex([4,5,6])
console.log(returnedSentence.sentence());
console.log(returnedSentence.sentence());
console.log(returnedSentence.sentence());

promises.js

// Challenge 1

function sayHello() {
	function printHello() {
    console.log('Challenge 1, 5', 'Hello');
  }
  setTimeout(printHello, 1000);
}

// Uncomment the line below when ready
sayHello(); // should log "Hello" after 1000ms


// Challenge 2
let promise = new Promise(function (resolve, reject) {
  // ADD CODE HERE
  setTimeout(resolve, 1000);
});

// Should print out "Resolved!"
// ADD CODE HERE
function displayResolve() {
	console.log('Challenge 2', 'Resolved!'); 
}
promise.then(displayResolve);


// Challenge 3

promise = new Promise(function(resolve, reject) {
  // ADD CODE HERE
  reject();
})

// Should print out "Reject!"
// ADD CODE HERE
function displayRejected() {
	console.log('Challenge 3', 'Rejected!'); 
}
promise.catch(displayRejected);


// Challenge 4

promise = new Promise(function (resolve, reject) {
  // ADD CODE HERE
  resolve();
});

// Uncomment the lines below when ready
promise.then(function () {
  console.log('Challenge 4', 'Promise has been resolved!')
});
console.log('Challenge 4', "I'm not the promise!");


// Challenge 5
function delay(){
	return new Promise(function (resolve, reject) {
		setTimeout(resolve, 1000);    
  });
}

// Uncomment the code below to test
// This code should log "Hello" after 1000ms
delay().then(sayHello);


// Challenge 6
//
// ADD CODE BELOW
const secondPromise = new Promise(function (resolve, reject) {
  resolve('Second!');
});
const firstPromise = new Promise(function (resolve, reject) {
  resolve(secondPromise);
})

firstPromise.then((value) => console.log('Challenge 6', value));


// Challenge 7
const fakePeople = [
  { name: 'Rudolph', hasPets: false, currentTemp: 98.6 },
  { name: 'Zebulon', hasPets: true, currentTemp: 22.6 },
  { name: 'Harold', hasPets: true, currentTemp: 98.3 },
]

const fakeAPICall = (i) => {
  const returnTime = Math.floor(Math.random() * 1000);
  return new Promise((resolve, reject) => {
    if (i >= 0 && i < fakePeople.length) {
      setTimeout(() => resolve(fakePeople[i]), returnTime);
    } else {
      reject({ message: "index out of range" });
    }
  });
};

function getAllData() {
  // CODE GOES HERE
  const apiPromises = [fakeAPICall(0), fakeAPICall(1), fakeAPICall(2)]
  return Promise.all(apiPromises)
  	.then(function(values) {
  		return values;
		});
}
  
getAllData().then((values) => console.log('Challenge 7', values));

In iterators.js > L157 seems have a let declaration as

for (let word of helloWorld) { console.log(word); } // -> should log 'Hello' and 'World'

However, the bug appears to be on Challenge 6 L105 on csbin.io which doesn't have let declaration for word when uncommented and run. I spent a lot of time figuring out the code in the placeholders left almost forgetting the test cases below uncommented lines.

UPDATE: I figured out that for...of loop may not have any declaration.

challenge #5

function delay(){
    return new Promise(function (resolve, reject) {
        setTimeout(resolve, 0);    // since the "sayHello" function at challenge 1 already waits for 1sec
  });
}

anyone have the solutions for iterators challenges 8 and 9?

for 8 it should be something like this

function* createConversation(str) {
yield setInterval(() => {
if (str == 'english') {
console.log('hello there')
} else {
console.log('gibberish');
}
}, 3000)
}

and for 9 should be similar to this

function waitForVerb(noun) {
return new Promise((resolve) => {
setTimeout(() => {
resolve(noun);
}, 3000);
})
}

async function f(noun) {
const result = await waitForVerb('good ');
console.log(result + noun)
}

f("dog");

onsole.log('hello there')
} else {
console.log('gibberish');
}
}, 3000)
}

we can simplify it by doing it like this,
console.log(string === 'english' ? 'hello there' : 'gibberish')

and for 9 should be similar to this

function waitForVerb(noun) { return new Promise((resolve) => { setTimeout(() => { resolve(noun); }, 3000); }) }

async function f(noun) { const result = await waitForVerb('good '); console.log(result + noun) }

f("dog");

I think for the challenge 9, if we follow the instructions (or I might be wrong), this is what's closest.

function waitForVerb(noun) {
  const verb = 'barks';
  return new Promise((resolve, reject) => {
    resolve(`${noun} ${verb}`);
  })
}

async function f(noun) {
  const sentence = await waitForVerb(noun);
  console.log(sentence)
}