16 KiB
16 KiB
| id | title | challengeType | forumTopicId |
|---|---|---|---|
| 587d7b8f367417b2b2512b61 | Use the map Method to Extract Data from an Array | 1 | 18214 |
Description
First Class Objects in JavaScript, which means they can be used like any other object. They can be saved in variables, stored in an object, or passed as function arguments.
Let's start with some simple array functions, which are methods on the array object prototype. In this exercise we are looking at Array.prototype.map(), or more simply map.
Remember that the map method is a way to iterate over each item in an array. It creates a new array (without changing the original one) after applying a callback function to every element.
Instructions
watchList array holds objects with information on several movies. Use map to pull the title and rating from watchList and save the new array in the rating variable. The code in the editor currently uses a for loop to do this, replace the loop functionality with your map expression.
Tests
tests:
- text: The <code>watchList</code> variable should not change.
testString: assert(watchList[0].Title === "Inception" && watchList[4].Director == "James Cameron");
- text: Your code should not use a <code>for</code> loop.
testString: assert(!removeJSComments(code).match(/for\s*?\(.*?\)/));
- text: Your code should use the <code>map</code> method.
testString: assert(code.match(/\.map/g));
- text: <code>rating</code> should equal <code>[{"title":"Inception","rating":"8.8"},{"title":"Interstellar","rating":"8.6"},{"title":"The Dark Knight","rating":"9.0"},{"title":"Batman Begins","rating":"8.3"},{"title":"Avatar","rating":"7.9"}]</code>.
testString: assert(JSON.stringify(rating) === JSON.stringify([{"title":"Inception","rating":"8.8"},{"title":"Interstellar","rating":"8.6"},{"title":"The Dark Knight","rating":"9.0"},{"title":"Batman Begins","rating":"8.3"},{"title":"Avatar","rating":"7.9"}]));
Challenge Seed
// the global variable
var watchList = [
{
"Title": "Inception",
"Year": "2010",
"Rated": "PG-13",
"Released": "16 Jul 2010",
"Runtime": "148 min",
"Genre": "Action, Adventure, Crime",
"Director": "Christopher Nolan",
"Writer": "Christopher Nolan",
"Actors": "Leonardo DiCaprio, Joseph Gordon-Levitt, Ellen Page, Tom Hardy",
"Plot": "A thief, who steals corporate secrets through use of dream-sharing technology, is given the inverse task of planting an idea into the mind of a CEO.",
"Language": "English, Japanese, French",
"Country": "USA, UK",
"Awards": "Won 4 Oscars. Another 143 wins & 198 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BMjAxMzY3NjcxNF5BMl5BanBnXkFtZTcwNTI5OTM0Mw@@._V1_SX300.jpg",
"Metascore": "74",
"imdbRating": "8.8",
"imdbVotes": "1,446,708",
"imdbID": "tt1375666",
"Type": "movie",
"Response": "True"
},
{
"Title": "Interstellar",
"Year": "2014",
"Rated": "PG-13",
"Released": "07 Nov 2014",
"Runtime": "169 min",
"Genre": "Adventure, Drama, Sci-Fi",
"Director": "Christopher Nolan",
"Writer": "Jonathan Nolan, Christopher Nolan",
"Actors": "Ellen Burstyn, Matthew McConaughey, Mackenzie Foy, John Lithgow",
"Plot": "A team of explorers travel through a wormhole in space in an attempt to ensure humanity's survival.",
"Language": "English",
"Country": "USA, UK",
"Awards": "Won 1 Oscar. Another 39 wins & 132 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BMjIxNTU4MzY4MF5BMl5BanBnXkFtZTgwMzM4ODI3MjE@._V1_SX300.jpg",
"Metascore": "74",
"imdbRating": "8.6",
"imdbVotes": "910,366",
"imdbID": "tt0816692",
"Type": "movie",
"Response": "True"
},
{
"Title": "The Dark Knight",
"Year": "2008",
"Rated": "PG-13",
"Released": "18 Jul 2008",
"Runtime": "152 min",
"Genre": "Action, Adventure, Crime",
"Director": "Christopher Nolan",
"Writer": "Jonathan Nolan (screenplay), Christopher Nolan (screenplay), Christopher Nolan (story), David S. Goyer (story), Bob Kane (characters)",
"Actors": "Christian Bale, Heath Ledger, Aaron Eckhart, Michael Caine",
"Plot": "When the menace known as the Joker wreaks havoc and chaos on the people of Gotham, the caped crusader must come to terms with one of the greatest psychological tests of his ability to fight injustice.",
"Language": "English, Mandarin",
"Country": "USA, UK",
"Awards": "Won 2 Oscars. Another 146 wins & 142 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BMTMxNTMwODM0NF5BMl5BanBnXkFtZTcwODAyMTk2Mw@@._V1_SX300.jpg",
"Metascore": "82",
"imdbRating": "9.0",
"imdbVotes": "1,652,832",
"imdbID": "tt0468569",
"Type": "movie",
"Response": "True"
},
{
"Title": "Batman Begins",
"Year": "2005",
"Rated": "PG-13",
"Released": "15 Jun 2005",
"Runtime": "140 min",
"Genre": "Action, Adventure",
"Director": "Christopher Nolan",
"Writer": "Bob Kane (characters), David S. Goyer (story), Christopher Nolan (screenplay), David S. Goyer (screenplay)",
"Actors": "Christian Bale, Michael Caine, Liam Neeson, Katie Holmes",
"Plot": "After training with his mentor, Batman begins his fight to free crime-ridden Gotham City from the corruption that Scarecrow and the League of Shadows have cast upon it.",
"Language": "English, Urdu, Mandarin",
"Country": "USA, UK",
"Awards": "Nominated for 1 Oscar. Another 15 wins & 66 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BNTM3OTc0MzM2OV5BMl5BanBnXkFtZTYwNzUwMTI3._V1_SX300.jpg",
"Metascore": "70",
"imdbRating": "8.3",
"imdbVotes": "972,584",
"imdbID": "tt0372784",
"Type": "movie",
"Response": "True"
},
{
"Title": "Avatar",
"Year": "2009",
"Rated": "PG-13",
"Released": "18 Dec 2009",
"Runtime": "162 min",
"Genre": "Action, Adventure, Fantasy",
"Director": "James Cameron",
"Writer": "James Cameron",
"Actors": "Sam Worthington, Zoe Saldana, Sigourney Weaver, Stephen Lang",
"Plot": "A paraplegic marine dispatched to the moon Pandora on a unique mission becomes torn between following his orders and protecting the world he feels is his home.",
"Language": "English, Spanish",
"Country": "USA, UK",
"Awards": "Won 3 Oscars. Another 80 wins & 121 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BMTYwOTEwNjAzMl5BMl5BanBnXkFtZTcwODc5MTUwMw@@._V1_SX300.jpg",
"Metascore": "83",
"imdbRating": "7.9",
"imdbVotes": "876,575",
"imdbID": "tt0499549",
"Type": "movie",
"Response": "True"
}
];
// Add your code below this line
var rating = [];
for(var i=0; i < watchList.length; i++){
rating.push({title: watchList[i]["Title"], rating: watchList[i]["imdbRating"]});
}
// Add your code above this line
console.log(JSON.stringify(rating));
After Test
const removeJSComments = str => str.replace(/\/\*[\s\S]*?\*\/|\/\/.*$/gm, '');
Solution
// the global variable
var watchList = [
{
"Title": "Inception",
"Year": "2010",
"Rated": "PG-13",
"Released": "16 Jul 2010",
"Runtime": "148 min",
"Genre": "Action, Adventure, Crime",
"Director": "Christopher Nolan",
"Writer": "Christopher Nolan",
"Actors": "Leonardo DiCaprio, Joseph Gordon-Levitt, Ellen Page, Tom Hardy",
"Plot": "A thief, who steals corporate secrets through use of dream-sharing technology, is given the inverse task of planting an idea into the mind of a CEO.",
"Language": "English, Japanese, French",
"Country": "USA, UK",
"Awards": "Won 4 Oscars. Another 143 wins & 198 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BMjAxMzY3NjcxNF5BMl5BanBnXkFtZTcwNTI5OTM0Mw@@._V1_SX300.jpg",
"Metascore": "74",
"imdbRating": "8.8",
"imdbVotes": "1,446,708",
"imdbID": "tt1375666",
"Type": "movie",
"Response": "True"
},
{
"Title": "Interstellar",
"Year": "2014",
"Rated": "PG-13",
"Released": "07 Nov 2014",
"Runtime": "169 min",
"Genre": "Adventure, Drama, Sci-Fi",
"Director": "Christopher Nolan",
"Writer": "Jonathan Nolan, Christopher Nolan",
"Actors": "Ellen Burstyn, Matthew McConaughey, Mackenzie Foy, John Lithgow",
"Plot": "A team of explorers travel through a wormhole in space in an attempt to ensure humanity's survival.",
"Language": "English",
"Country": "USA, UK",
"Awards": "Won 1 Oscar. Another 39 wins & 132 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BMjIxNTU4MzY4MF5BMl5BanBnXkFtZTgwMzM4ODI3MjE@._V1_SX300.jpg",
"Metascore": "74",
"imdbRating": "8.6",
"imdbVotes": "910,366",
"imdbID": "tt0816692",
"Type": "movie",
"Response": "True"
},
{
"Title": "The Dark Knight",
"Year": "2008",
"Rated": "PG-13",
"Released": "18 Jul 2008",
"Runtime": "152 min",
"Genre": "Action, Adventure, Crime",
"Director": "Christopher Nolan",
"Writer": "Jonathan Nolan (screenplay), Christopher Nolan (screenplay), Christopher Nolan (story), David S. Goyer (story), Bob Kane (characters)",
"Actors": "Christian Bale, Heath Ledger, Aaron Eckhart, Michael Caine",
"Plot": "When the menace known as the Joker wreaks havoc and chaos on the people of Gotham, the caped crusader must come to terms with one of the greatest psychological tests of his ability to fight injustice.",
"Language": "English, Mandarin",
"Country": "USA, UK",
"Awards": "Won 2 Oscars. Another 146 wins & 142 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BMTMxNTMwODM0NF5BMl5BanBnXkFtZTcwODAyMTk2Mw@@._V1_SX300.jpg",
"Metascore": "82",
"imdbRating": "9.0",
"imdbVotes": "1,652,832",
"imdbID": "tt0468569",
"Type": "movie",
"Response": "True"
},
{
"Title": "Batman Begins",
"Year": "2005",
"Rated": "PG-13",
"Released": "15 Jun 2005",
"Runtime": "140 min",
"Genre": "Action, Adventure",
"Director": "Christopher Nolan",
"Writer": "Bob Kane (characters), David S. Goyer (story), Christopher Nolan (screenplay), David S. Goyer (screenplay)",
"Actors": "Christian Bale, Michael Caine, Liam Neeson, Katie Holmes",
"Plot": "After training with his mentor, Batman begins his fight to free crime-ridden Gotham City from the corruption that Scarecrow and the League of Shadows have cast upon it.",
"Language": "English, Urdu, Mandarin",
"Country": "USA, UK",
"Awards": "Nominated for 1 Oscar. Another 15 wins & 66 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BNTM3OTc0MzM2OV5BMl5BanBnXkFtZTYwNzUwMTI3._V1_SX300.jpg",
"Metascore": "70",
"imdbRating": "8.3",
"imdbVotes": "972,584",
"imdbID": "tt0372784",
"Type": "movie",
"Response": "True"
},
{
"Title": "Avatar",
"Year": "2009",
"Rated": "PG-13",
"Released": "18 Dec 2009",
"Runtime": "162 min",
"Genre": "Action, Adventure, Fantasy",
"Director": "James Cameron",
"Writer": "James Cameron",
"Actors": "Sam Worthington, Zoe Saldana, Sigourney Weaver, Stephen Lang",
"Plot": "A paraplegic marine dispatched to the moon Pandora on a unique mission becomes torn between following his orders and protecting the world he feels is his home.",
"Language": "English, Spanish",
"Country": "USA, UK",
"Awards": "Won 3 Oscars. Another 80 wins & 121 nominations.",
"Poster": "http://ia.media-imdb.com/images/M/MV5BMTYwOTEwNjAzMl5BMl5BanBnXkFtZTcwODc5MTUwMw@@._V1_SX300.jpg",
"Metascore": "83",
"imdbRating": "7.9",
"imdbVotes": "876,575",
"imdbID": "tt0499549",
"Type": "movie",
"Response": "True"
}
];
var rating = watchList.map(function(movie) {
return {
title: movie["Title"],
rating: movie["imdbRating"]
}
});