As a personal challenge to learn and grow my JavaScript skills, I will be digging into some of the most popular methods and properties the language has to offer. Over the next several weeks, I will be completing a series of algorithm challenges that require the use of specific methods/properties.
The first method in my challenge is filter().
According to the Mozilla documentation:
The Javascript array filter() creates a new array of elements from an existing array that meets a specified condition.
Time Complexity: O(n)
I decided to challenge myself with the .filter() method first because it's super useful when it comes to dealing with data. Pretty much every website with a catalogue of data (products, articles, users, etc.) needs a way to filter and return only the data necessary to perform an action. I know I have done many web searches and used the handy filtering options to narrow down the results to find exactly what I want.
If you've never used the filter() method, check out this awesome documentation from GeeksforGeeks for more information.
Challenge: Filter An Array of Objects
// create a function that filters an array of objects to find hotels rated at least N stars or higher const data = [ { name: 'Hilton', rating: 4.7 }, { name: 'Best Western', rating: 3.8 }, { name: 'Bob\'s Hotel', rating: 2.5 }, { name: 'Marriot', rating: 4.2 } ]; function filterByRating(data, ratingMinimum, ratingMaximum) { data = data.filter(data => data.rating >= (ratingMinimum ?? 0)); data = data.filter(data => data.rating <= (ratingMaximum ?? 5)); return data; } const hotelsWithAtLeast4Stars = filterByRating(data, 4); console.log(hotelsWithAtLeast4Stars); // OUTPUT // [{ name: 'Hilton', rating: 4.7 }, { name: 'Marriot', rating: 4.2 } ] const hotelsWithAtLeast3Stars = filterByRating(data, 3); console.log(hotelsWithAtLeast3Stars); // OUTPUT // [ // { name: 'Hilton', rating: 4.7 }, // { name: 'Best Western', rating: 3.8 }, // { name: 'Marriot', rating: 4.2 } // ] const hotelsBetween3and4Stars = filterByRating(data, 3, 4); console.log(hotelsBetween3and4Stars); // OUTPUT // [ { name: 'Best Western', rating: 3.8 } ] const hotelsWith3orLessStars = filterByRating(data, null, 3); console.log(hotelsWith3orLessStars); // OUTPUT // [ { name: "Bob's Hotel", rating: 2.5 } ] Challenge: Filter An Array of Numbers/Strings
// Challenge #1 // Create a function that filters strings by length given two arguments: minimum length, maximum length // Either argument may be missing. if both are missing, return the original array function filterStringsByLength(arrayOfStrings, minLength, maxLength) { arrayOfStrings = arrayOfStrings.filter(string => string.length >= (minLength ?? 0)); arrayOfStrings = arrayOfStrings.filter(string => string.length <= (maxLength ?? string.length)); return arrayOfStrings; } const arrayOfStrings = ['', 'a', 'bc', 'def', 'ghij', 'klmno', 'pqrstu', 'vwxyz12']; const nums = [1,2,3,4,5] const wordsAtLeast3Characters = filterStringsByLength(arrayOfStrings, 3); console.log(wordsAtLeast3Characters); // OUTPUT // [ 'def', 'ghij', 'klmno', 'pqrstu', 'vwxyz12' ] const wordsNoLongerThan5Characters = filterStringsByLength(arrayOfStrings, null, 5); console.log(wordsNoLongerThan5Characters); // OUTPUT // [ '', 'a', 'bc', 'def', 'ghij', 'klmno' ] const wordsAtLeast3CharactersAndNoLongerThan5Characters = filterStringsByLength(arrayOfStrings, 3, 5); console.log(wordsAtLeast3CharactersAndNoLongerThan5Characters); // OUTPUT // [ 'def', 'ghij', 'klmno' ] let minAndMaxNotProvided = filterStringsByLength(arrayOfStrings); console.log(minAndMaxNotProvided); // OUTPUT // ['', 'a', 'bc', 'def', 'ghij', 'klmno', 'pqrstu', 'vwxyz12'] // Challenge #2 // Create a function that filters an array of numbers, given two arguments: minimum and maximum. // Either argument may be missing. if both are missing, return the original array function filterNumbersBySize(arrayOfNumbers, minSize, maxSize) { arrayOfNumbers = arrayOfNumbers.filter(number => number >= (minSize ?? number)); arrayOfNumbers = arrayOfNumbers.filter(number => number <= (maxSize ?? number)); return arrayOfNumbers; } const arrayOfNumbers = [-12, -4, 0, 2, 11, 63, 1001]; const numbersMinus5AndUp = filterNumbersBySize(arrayOfNumbers, -5); console.log(numbersMinus5AndUp); // OUTPUT // [ -4, 0, 2, 11, 63, 1001 ] const numbersNoGreaterThan10 = filterNumbersBySize(arrayOfNumbers, null, 10); console.log(numbersNoGreaterThan10); // OUTPUT // [ -12, -4, 0, 2 ] const numbersBetweenMinus4And11 = filterNumbersBySize(arrayOfNumbers, -4, 11); console.log(numbersBetweenMinus4And11); // OUTPUT // [ -4, 0, 2, 11 ] minAndMaxNotProvided = filterNumbersBySize(arrayOfNumbers); console.log(minAndMaxNotProvided); // OUTPUT // [-12, -4, 0, 2, 11, 63, 1001] Challenge: Filter Out Repeated Values
// Write a function to filter out any duplicates in an array // Input type is an array of strings and/or numbers function removeDuplicates(array) { return array.filter((item, index) => index === array.indexOf(item)); } const arrayOfStrings = ['aa', 'bb', 'cc', 'dd', 'ee', 'aa', 'bb', 'cc']; const arrayOfStringsWithoutDupes = removeDuplicates(arrayOfStrings); console.log(arrayOfStringsWithoutDupes); // OUTPUT // [ 'aa', 'bb', 'cc', 'dd', 'ee' ] const arrayOfNumbers = [0, 1, 1, 2, 3, 3, 3, 4, 5]; const arrayOfNumbersWithoutDupes = removeDuplicates(arrayOfNumbers); console.log(arrayOfNumbersWithoutDupes); // OUTPUT // [ 0, 1, 2, 3, 4, 5 ] const arrayOfNumbersAndStrings = arrayOfStrings.concat(arrayOfNumbers); const arrayOfNumbersAndStringsWithoutDupes = removeDuplicates(arrayOfNumbersAndStrings); console.log(arrayOfNumbersAndStringsWithoutDupes); // OUTPUT // [ 'aa', 'bb', 'cc', 'dd', 'ee', 0, 1, 2, 3, 4, 5 ] 
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