count-sum-version-2.js

// Here's another solution I made previously using some fancy reduce stuff to make me look cool
// https://www.codewars.com/kata/576bb71bbbcf0951d5000044/train/javascript

function countPositivesSumNegatives(input) {
  if(!input || input.length === 0) return [];
  return input.reduce(
    (result, num) => (num > 0) ? [++result[0], result[1]] : [result[0], result[1] + num],
    [0, 0]
  )
}

count-sum.js

// https://www.codewars.com/kata/576bb71bbbcf0951d5000044/train/javascript

function countPositivesSumNegatives(input) {
  // Handle empty or null inputs
  if(input === null || input.length === 0)
    return [];
  
  // We could save these in variables, or we could just put them right on lines 13 and 15
  // const positives = input.filter(number => number > 0);
  // const negatives = input.filter(number => number < 0);
  
  // count all the positives
  const positiveCount = input.filter(number => number > 0).length;
  // sum all the negatives
  const negativeSum = input.filter(number => number < 0).reduce((total, number) => total + number, 0);
  
  return [positiveCount, negativeSum];
}

disemvowel-trolls.js

// https://www.codewars.com/kata/52fba66badcd10859f00097e/train/javascript

const VOWELS = ["a", "e", "i", "o", "u", "A", "E", "I", "O", "U"];
function disemvowel(str) {
  return str.split('').filter(character => !VOWELS.includes(character)).join('');  
}

// We could write isVowel like this:
//const isVowel = (character) => VOWELS.includes(character.toLowerCase());

// Or if brevity is more important than simplicity, like this:
//const isVowel = (character) => ["a", "e", "i", "o", "u"].includes(character.toLowerCase());

// We could solve it with a for loop
// function disemvowel(str) {
//   let result = "";
//   for(let i = 0; i < str.length; i++) {
//     if( !isVowel( str[i] ) ) {
//        result += str[i];
//     }
//   }
//   return result;
// }

// Or with array methods
// function disemvowel(str) {
//   const characters = str.split('');
//   const result = characters.filter(character => !isVowel(character))
//   return result.join('');
// }

// And simplify it down
// function disemvowel(str) {
//   return str.split('').filter(character => !isVowel(character)).join('');
// }

happy-birthday.js

// https://www.codewars.com/kata/5d65fbdfb96e1800282b5ee0/train/javascript

function wrap(height, width, length){
  const dimensions = [height, width, length].sort((a, b) => a - b)
  return (2 * dimensions[2]) + (2 * dimensions[1]) + (4 * dimensions[0]) + 20;
}

// Some of our thought process, I often might write this on a piece of paper as I thought it through
// 2 x biggest
// 2 x middle
// 4 x smallest
// 20

// A less compact but maybe more readable solution?
// function wrap(height, width, length){
//   const dimensions = [height, width, length].sort((a, b) => a - b)
//   const biggest = dimensions[2];
//   const middle = dimensions[1];
//   const smallest = dimensions[0];
//   return (2 * biggest) + (2 * middle) + (4 * smallest) + 20;
// }

// A definitely overcomplicated, but let us play around with array methods solution :)
// function wrap(height, width, length){
//   const dimensions = [height, width, length].sort((a, b) => a - b)
//   dimensions.push(dimensions[0])
//   return dimensions.map(number => number * 2).reduce((total, number) => total + number) + 20
// }

// An example of how .map() and .reduce() together can be really useful!
// const cartItems = [
//   {
//     name: "Toilet paper",
//     price: 200
//   },
//   {
//     name: "Paper towels",
//     price: 300
//   }
// ]
// const total = cartItems.map(item => item.price).reduce((total, number) => total + number)