Jose Linardo
3 years ago
parent
cb12fc2c65
commit
d35a807502
@ -1,2 +1,202 @@
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console.log(countries)
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alert('Open the console and check if the countries has been loaded')
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//alert('Open the console and check if the countries has been loaded')
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//Exercises.
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//Exercises: Level 1
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const countries_ = ['Finland', 'Sweden', 'Denmark', 'Norway', 'IceLand']
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const names = ['Asabeneh', 'Mathias', 'Elias', 'Brook']
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const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
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const products = [
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{ product: 'banana', price: 3 },
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{ product: 'mango', price: 6 },
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{ product: 'potato', price: ' ' },
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{ product: 'avocado', price: 8 },
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{ product: 'coffee', price: 10 },
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{ product: 'tea', price: '' },
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]
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//1. Explain the difference between forEach, map, filter, and reduce.
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//forEach() itera sobre cada elemento del array y le aplica la cuncion callback, no retorna nada a diferencia de map(); el metodo map() recorre la matriz y devuelve una nueva matriz modificada con la condiciones dadas en la funcion cb podria decir que aplica la funcion callback a cada elemento del array. el metodo filter()recorre el array y filtra los objetos que cumplan con la condicion de la funcion callback recibe tres parametros elemento, el indice y el array estos dos ultimos son opcionales. el metodo reduce() recibe dos parametros un acumulador acc y un valor actual curr al final retorna el acumulador, es decir el valor acumulado de cada elemento curr
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//2. Define a callback function before you use it in forEach, map, filter or reduce.
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function callback (element) {
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console.log(element)
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}
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function uppercase (element) {
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return element.toUpperCase()
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}
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//3. Use forEach to console.log each country in the countries array.
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countries_.forEach(callback)
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//4. Use forEach to console.log each name in the names array.
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names.forEach(callback)
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//5. Use forEach to console.log each number in the numbers array.
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numbers.forEach(callback)
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//6. Use map to create a new array by changing each country to uppercase in the countries array.
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const newUpperCaseArray = countries_.map(uppercase)
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console.log(newUpperCaseArray)
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//7. Use map to create an array of countries length from countries array.
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const newCountriesArray = countries_.map(el => el)
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console.log(newCountriesArray)
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//8. Use map to create a new array by changing each number to square in the numbers array
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let numbersToSquare = numbers.map(el => el ** 2)
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console.log(numbersToSquare)
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//9. Use map to change to each name to uppercase in the names array
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console.log(names.map(el => el.toUpperCase()))
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//10. Use map to map the products array to its corresponding prices.
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const corresponding = products.map(el => {
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let newObj = []
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newObj.push( el.product, el.price)
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return newObj
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})
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console.log(corresponding)
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//11. Use filter to filter out countries containing land.
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console.log(countries.filter(el => el.name.includes('land')))
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//12 Use filter to filter out countries having six character.
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console.log(countries.filter(el => el.name.length === 6))
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//13.Use filter to filter out countries containing six letters and more in the country array.
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console.log(countries.filter(el => el.name.length >= 6))
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//14. Use filter to filter out country start with 'E';
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console.log(countries.filter(el => el.name.startsWith('E')))
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//15. Use filter to filter out only prices with values.
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const pricesValues = products.filter(el => typeof el.price === 'number')
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console.log(pricesValues)
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//16 Declare a function called getStringLists which takes an array as a parameter and then returns an array only with string items.
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let arrMix = [1,'Hola', 23, 'Mundo', 45, 2]
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function getStringLists (arr) {
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return arr.filter(el => typeof el === 'string')
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}
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//17. Use reduce to sum all the numbers in the numbers array.
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console.log(numbers.reduce((acc, curr) => acc + curr))
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//18. Use reduce to concatenate all the countries and to produce this sentence: Estonia, Finland, Sweden, Denmark, Norway, and IceLand are north European countries
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const concatenateCountries = countries.reduce((acc, curr) => {
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return acc.concat(curr.name)
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},[])
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console.log(concatenateCountries)
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//19. Explain the difference between some and every
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// some() recorre el array y comprueba si al menos un elemento cumple con la o las condiciones de la funcion callback retorna un booleano y devuleve false en un array vacio
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// el metodo every() a direrencia de some comprueba si todos los elementos del array satisfacen la condicion de la funcion callback
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//20. Use some to check if some names' length greater than seven in names array
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console.log(names.some(el => el.length > 7))
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//21.Use every to check if all the countries contain the word land
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console.log(countries_.every(el => el.includes('land')))
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//22. Explain the difference between find and findIndex.
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// find() retorna el primer valor del elemento que satisface la condicion dada en la funcion callback, mientras que findIndex() retorna el primer indice del elemento que satisface la condicion de la funcion. find retorna el valor y findIdex el indice
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//23. Use find to find the first country containing only six letters in the countries array
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console.log(countries_.find(el => el.length === 6 ))
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//24. Use findIndex to find the position of the first country containing only six letters in the countries array
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console.log(countries_.findIndex(el => el.length === 6 ))
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//25. Use findIndex to find the position of Norway if it doesn't exist in the array you will get -1.
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console.log(countries_.findIndex(el => el ==='Norway' ))
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//26. Use findIndex to find the position of Russia if it doesn't exist in the array you will get -1.
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console.log(countries_.findIndex(el => el ==='Russia' ))
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//Exercises: Level 2
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//Find the total price of products by chaining two or more array
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//iterators(eg. arr.map(callback).filter(callback).reduce(callback))
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let sumPricePoducts = products.filter(el => typeof el.price === 'number').reduce((acc, curr) => acc + curr.price,0)//27
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console.log(`the total sum of prices from products is ${sumPricePoducts}`)
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//2. Find the sum of price of products using only reduce reduce(callback))
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console.log(products.filter(el => typeof el.price === 'number').reduce((acc, curr) => acc + curr.price,0))
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//3.Declare a function called categorizeCountries which returns an array of countries which have some common pattern(you find the countries array in this repository as countries.js(eg 'land', 'ia', 'island','stan')).
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function categorizeCountries(arr) {
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const pattern = ['land', 'ia', 'Island', 'stan'];
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const categorized = [];
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pattern.forEach((element) => {
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const sort = [];
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//use string template
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let category = `${element}`;
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categorized.push(arr.filter((country) =>
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country.includes(`${element}`)))
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});
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return categorized;
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}
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console.log(categorizeCountries(concatenateCountries));
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//4. Create a function which return an array of objects, which is the letter and the number of times the letter use to start with a name of a country.
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function initialAndTimes(arr) {
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const array = [];
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const abc = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];
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abc.forEach((letter) => {
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const object = {};
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object.letter = `${letter}`;
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object.times = arr.filter((country) =>
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country.startsWith(`${letter}`)).length;
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array.push(object);
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})
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return array;
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}
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console.log(initialAndTimes(concatenateCountries));
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//5. Declare a getFirstTenCountries function and return an array of ten countries. Use different functional programming to work on the countries.js array
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function getFirstTenCountries() {
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const firstTenCountries = countries.filter((element) => {
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return countries.indexOf(element) < 10;
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})
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return firstTenCountries;
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}
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console.log(getFirstTenCountries());
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//6. Declare a getLastTenCountries function which which returns the last ten countries in the countries array.
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function getLastTenCountries() {
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const lastTenCountries = countries.filter((element) =>
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countries.indexOf(element) > countries.length - 11
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)
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return lastTenCountries;
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}
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console.log(getLastTenCountries());
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//7. Find out which letter is used many times as initial for a country name from the countries array (eg. Finland, Fiji, France etc)
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function mostUsedInitial(arr) {
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const abc = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];
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const initial = [];
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abc.forEach((letter) => {
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let initialNum = arr.filter((country) =>
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country.startsWith(`${letter}`)).length;
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initial.push(initialNum);
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})
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let max = Math.max(...initial);
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let index = initial.indexOf(max);
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return abc[index];
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}
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console.log(mostUsedInitial(concatenateCountries));
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// Exercises: Level 3
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