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@aegorenkov
Created July 26, 2018 22:23
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HardParts Promises and Iterators
// 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());
// 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));
@Peter-AMD
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Peter-AMD commented Aug 28, 2023

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)
}

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