Amazon Rd. 1 Interview questions

amazon_interview.js

// Non-coding questions
// 1. Describe what happens in the Browser after a user enters a URL and hits enter.
// 2. Describe what is a XSS (Cross-site scripting) attack and how can we prevent them?

// Coding question 1
// Given an array of strings, return an array with all duplicates removed
// ex: ['a', 'a', 'a', 'b', 'a', 'c', 'c'] => ['a', 'b', 'c']

//Solution #1:
const dedupeArray = (array = []) => {
  const result = [];
  array.forEach((letter) => {
    if (!result.includes(letter)) {
      result.push(letter);
    }
  })
  
  return result
}

//Solution #2:
const dedupeArray = (array = []) => {
  const counter = {};
  array.forEach((letter) => {
    if (!counter[letter])) {
      counter[letter] = true;
    }
  })
  
  return Object.keys(counter)
}

// Coding question 2
// Given a string, return a new string with the unique letters in order of most frequent to least frequent. 
// (handle Spaces and punction as you would any other character)

const frequencyCounter = (string) => {
  const counter = {}
  
  string.split('').forEach((char) => {
    if (char in counter) {
      counter[char] ++;
    } else {
      counter[char] = 1;
    }
  })
  
  // Grab array of entries, sort by value, and then map back keys in sorted order
  return Object.entries(counter)
            .sort((a, b) => b[1] - a[1])
            .map(entry => entry[0])
            .join('')
}