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| 1 | +/*Promises in Javascript |
| 2 | +A promise is an object that may produce a single value some time in the future: either a resolved value, or a reason that it’s not resolved (e.g., a network error occurred). A promise may be in one of 3 possible states: fulfilled, rejected, or pending. Promise users can attach callbacks to handle the fulfilled value or the reason for rejection. |
| 3 | + |
| 4 | + |
| 5 | + |
| 6 | +Problem Description |
| 7 | +Given as inputs to the getLastNames() function |
| 8 | + |
| 9 | +A string representing a first name, firstName. |
| 10 | +An Array of person objects with properties, "firstName" and "lastName" |
| 11 | + |
| 12 | + |
| 13 | +Return a JavaScript Promise which is either |
| 14 | +rejected with a message "Invalid" if none of the person objects "firstName" property matches the input first name, firstName |
| 15 | +resolved with an sorted Array of "lastName" property values of objects whose "firstName" property matches the given first name, firstName |
| 16 | + |
| 17 | +Note |
| 18 | + |
| 19 | +The "lastName"s array should be sorted in alphabetical order |
| 20 | + |
| 21 | +Function to return a Promise object and not a String or Array |
| 22 | +*/ |
| 23 | + |
| 24 | +function getLastNames(firstName, people) { |
| 25 | + |
| 26 | + return new Promise(function (resolve, reject) { |
| 27 | + let matchingPeeps = []; |
| 28 | + matchingPeeps = people.filter((obj) => { |
| 29 | + return obj.firstName === firstName |
| 30 | + }) |
| 31 | + |
| 32 | + if (matchingPeeps.length === 0) { |
| 33 | + reject("Invalid"); |
| 34 | + } else { |
| 35 | + let unsortedArray = []; |
| 36 | + |
| 37 | + for (let i = 0; i < matchingPeeps.length; i++) { |
| 38 | + let lastName = matchingPeeps[i].lastName; |
| 39 | + unsortedArray.push(lastName); |
| 40 | + } |
| 41 | + unsortedArray.sort(); |
| 42 | + resolve(unsortedArray); |
| 43 | + } |
| 44 | + }) |
| 45 | +} |
| 46 | + |
| 47 | + |
| 48 | +let firstName = 'David' |
| 49 | + |
| 50 | +people = [ |
| 51 | + |
| 52 | + { |
| 53 | + |
| 54 | + firstName: 'David', |
| 55 | + |
| 56 | + lastName: 'Dobrick' |
| 57 | + |
| 58 | + }, |
| 59 | + |
| 60 | + { |
| 61 | + |
| 62 | + firstName: 'David', |
| 63 | + |
| 64 | + lastName: 'Beckham' |
| 65 | + |
| 66 | + }, |
| 67 | + |
| 68 | + { |
| 69 | + |
| 70 | + firstName: 'Chris', |
| 71 | + |
| 72 | + lastName: 'Lee' |
| 73 | + |
| 74 | + }, |
| 75 | + |
| 76 | + { |
| 77 | + |
| 78 | + firstName: 'James', |
| 79 | + |
| 80 | + lastName: 'Bond' |
| 81 | + |
| 82 | + }, |
| 83 | + |
| 84 | +] |
| 85 | + |
| 86 | +console.log(getLastNames(firstName, people)) |
| 87 | +module.exports = getLastNames; |
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