Promises

const Promise = require('bluebird'); const locations = ['Boston', 'Dallas', 'Houston', 'Miami', 'New York', 'San Francisco']; const names = ['Bob', 'John', 'Margaret', 'Tara']; function getPersonalInfo(key) { const random = Math.random(); const person = { age : Math.round(random * 100), location : Math.floor(random * locations.length), name : Math.floor(random * names.length), }; return Promise.resolve(person[key]); } // Using the above, write a function that returns a promise that resolves with `person` (an object representing a person's age, location, and name. Ignore the fact that we construct a person object with each invokation of getPersonalInfo. // Solution function getRandomPerson() { return Promise.join(getPersonalInfo('age'), getPersonalInfo('location'), getPersonalInfo('name')) .spread((age, location, name) => { age, location, name }); } ////////////////////////////////////////////////////////////////////// // Write a function that returns a promise that resolves around n second later after invoked with any value. // Solution 1 function getAfterNSeconds(n) { return new Promise((resolve) => setTimeout(() => resolve(), n)); } // Solution 2 function getAfterNSeconds(n) { return Promise.resolve().delay(n); } ////////////////////////////////////////////////////////////////////// const numbers = [1, 2, 3, 4, 5]; // Write a function that serially consumes the above data and multiplies each data point by n. The function should return a promise resolving with an array of the new values. // Solution function multiply(n) { return Promise.mapSeries(numbers, (number) => number * n); } ////////////////////////////////////////////////////////////////////// const multipliers = [2, 4, 8, 16]; const startNumber = 1; // Using the above function, write a function that returns a promise resulting with the aggregate of multiplying startNumber with the provided multipliers. Note that the number should be getting bigger than the multipliers as you go through multipliers. // Solution function aggregate(num, multiples) { return Promise.reduce(multiples, (mult, agg) => mult * agg, num); }