176 lines
9.1 KiB
Markdown
176 lines
9.1 KiB
Markdown
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---
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id: 587d7da9367417b2b2512b68
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title: Use the reduce Method to Analyze Data
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challengeType: 1
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videoUrl: ''
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localeTitle: Use o método de redução para analisar dados
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---
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## Description
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<section id="description"> <code>Array.prototype.reduce()</code> , ou simplesmente <code>reduce()</code> , é a mais geral de todas as operações de array em JavaScript. Você pode resolver quase qualquer problema de processamento de matriz usando o método <code>reduce</code> . Este não é o caso dos métodos <code>filter</code> e <code>map</code> , pois eles não permitem a interação entre dois elementos diferentes da matriz. Por exemplo, se você quiser comparar elementos da matriz ou adicioná-los juntos, o <code>filter</code> ou o <code>map</code> não poderão processá-los. O método <code>reduce</code> permite formas mais gerais de processamento de array, e é possível mostrar que tanto o <code>filter</code> quanto o <code>map</code> podem ser derivados como uma aplicação especial de <code>reduce</code> . No entanto, antes de chegarmos lá, vamos praticar o uso de <code>reduce</code> primeiro. </section>
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## Instructions
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<section id="instructions"> A variável <code>watchList</code> contém uma matriz de objetos com informações sobre vários filmes. Use <code>reduce</code> para encontrar a classificação média do IMDB dos filmes <strong>dirigidos por Christopher Nolan</strong> . Lembre-se de desafios anteriores de como <code>filter</code> dados e <code>map</code> -los para extrair o que você precisa. Talvez seja necessário criar outras variáveis, mas salve a média final na variável <code>averageRating</code> . Observe que os valores de classificação são salvos como sequências no objeto e precisam ser convertidos em números antes de serem usados em qualquer operação matemática. </section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: A variável <code>watchList</code> não deve mudar.
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testString: 'assert(watchList[0].Title === "Inception" && watchList[4].Director == "James Cameron", "The <code>watchList</code> variable should not change.");'
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- text: Seu código deve usar o método <code>reduce</code> .
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testString: 'assert(code.match(/\.reduce/g), "Your code should use the <code>reduce</code> method.");'
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- text: O <code>averageRating</code> deve ser igual a 8.675.
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testString: 'assert(averageRating == 8.675, "The <code>averageRating</code> should equal 8.675.");'
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- text: Seu código não deve usar um loop <code>for</code> .
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testString: 'assert(!code.match(/for\s*?\(.*\)/g), "Your code should not use a <code>for</code> loop.");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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// the global variable
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var watchList = [
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{
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"Title": "Inception",
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"Year": "2010",
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"Rated": "PG-13",
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"Released": "16 Jul 2010",
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"Runtime": "148 min",
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"Genre": "Action, Adventure, Crime",
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"Director": "Christopher Nolan",
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"Writer": "Christopher Nolan",
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"Actors": "Leonardo DiCaprio, Joseph Gordon-Levitt, Ellen Page, Tom Hardy",
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"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.",
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"Language": "English, Japanese, French",
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"Country": "USA, UK",
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"Awards": "Won 4 Oscars. Another 143 wins & 198 nominations.",
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"Poster": "http://ia.media-imdb.com/images/M/MV5BMjAxMzY3NjcxNF5BMl5BanBnXkFtZTcwNTI5OTM0Mw@@._V1_SX300.jpg",
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"Metascore": "74",
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"imdbRating": "8.8",
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"imdbVotes": "1,446,708",
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"imdbID": "tt1375666",
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"Type": "movie",
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"Response": "True"
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},
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{
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"Title": "Interstellar",
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"Year": "2014",
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"Rated": "PG-13",
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"Released": "07 Nov 2014",
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"Runtime": "169 min",
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"Genre": "Adventure, Drama, Sci-Fi",
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"Director": "Christopher Nolan",
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"Writer": "Jonathan Nolan, Christopher Nolan",
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"Actors": "Ellen Burstyn, Matthew McConaughey, Mackenzie Foy, John Lithgow",
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"Plot": "A team of explorers travel through a wormhole in space in an attempt to ensure humanity's survival.",
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"Language": "English",
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"Country": "USA, UK",
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"Awards": "Won 1 Oscar. Another 39 wins & 132 nominations.",
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"Poster": "http://ia.media-imdb.com/images/M/MV5BMjIxNTU4MzY4MF5BMl5BanBnXkFtZTgwMzM4ODI3MjE@._V1_SX300.jpg",
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"Metascore": "74",
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"imdbRating": "8.6",
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"imdbVotes": "910,366",
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"imdbID": "tt0816692",
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"Type": "movie",
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"Response": "True"
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},
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{
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"Title": "The Dark Knight",
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"Year": "2008",
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"Rated": "PG-13",
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"Released": "18 Jul 2008",
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"Runtime": "152 min",
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"Genre": "Action, Adventure, Crime",
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"Director": "Christopher Nolan",
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"Writer": "Jonathan Nolan (screenplay), Christopher Nolan (screenplay), Christopher Nolan (story), David S. Goyer (story), Bob Kane (characters)",
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"Actors": "Christian Bale, Heath Ledger, Aaron Eckhart, Michael Caine",
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"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.",
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"Language": "English, Mandarin",
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"Country": "USA, UK",
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"Awards": "Won 2 Oscars. Another 146 wins & 142 nominations.",
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"Poster": "http://ia.media-imdb.com/images/M/MV5BMTMxNTMwODM0NF5BMl5BanBnXkFtZTcwODAyMTk2Mw@@._V1_SX300.jpg",
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"Metascore": "82",
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"imdbRating": "9.0",
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"imdbVotes": "1,652,832",
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"imdbID": "tt0468569",
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"Type": "movie",
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"Response": "True"
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},
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{
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"Title": "Batman Begins",
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"Year": "2005",
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"Rated": "PG-13",
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"Released": "15 Jun 2005",
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"Runtime": "140 min",
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"Genre": "Action, Adventure",
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"Director": "Christopher Nolan",
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"Writer": "Bob Kane (characters), David S. Goyer (story), Christopher Nolan (screenplay), David S. Goyer (screenplay)",
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"Actors": "Christian Bale, Michael Caine, Liam Neeson, Katie Holmes",
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"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.",
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"Language": "English, Urdu, Mandarin",
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"Country": "USA, UK",
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"Awards": "Nominated for 1 Oscar. Another 15 wins & 66 nominations.",
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"Poster": "http://ia.media-imdb.com/images/M/MV5BNTM3OTc0MzM2OV5BMl5BanBnXkFtZTYwNzUwMTI3._V1_SX300.jpg",
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"Metascore": "70",
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"imdbRating": "8.3",
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"imdbVotes": "972,584",
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"imdbID": "tt0372784",
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"Type": "movie",
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"Response": "True"
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},
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{
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"Title": "Avatar",
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"Year": "2009",
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"Rated": "PG-13",
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"Released": "18 Dec 2009",
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"Runtime": "162 min",
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"Genre": "Action, Adventure, Fantasy",
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"Director": "James Cameron",
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"Writer": "James Cameron",
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"Actors": "Sam Worthington, Zoe Saldana, Sigourney Weaver, Stephen Lang",
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"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.",
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"Language": "English, Spanish",
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"Country": "USA, UK",
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"Awards": "Won 3 Oscars. Another 80 wins & 121 nominations.",
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"Poster": "http://ia.media-imdb.com/images/M/MV5BMTYwOTEwNjAzMl5BMl5BanBnXkFtZTcwODc5MTUwMw@@._V1_SX300.jpg",
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"Metascore": "83",
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"imdbRating": "7.9",
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"imdbVotes": "876,575",
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"imdbID": "tt0499549",
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"Type": "movie",
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"Response": "True"
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}
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];
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// Add your code below this line
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var averageRating;
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// Add your code above this line
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console.log(averageRating);
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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