kata-7-solution-square-every-digit.js

/*
 * Square Every Digit
 * https://www.codewars.com/kata/546e2562b03326a88e000020
 */


// Solution 1
// toString - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString
// join - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/join 
function squareDigits(num){
  let string = num.toString();  // turn number to a string
  let results = [];             // create an array to save the new values of the string
  for (let i = 0; i < string.length; i++){  // iterate through the string
      results[i] = string[i] * string[i];   // save the square of the number to the array 
  }
  return Number(results.join(''));    // turn the array into a string and then into a number
}

// Solution 2 
// parseInt - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt 
// split - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/split 
// map - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map  
function squareDigits(num){
  let array = num.toString().split('').map( function(int) {   // turn number to string then make string to array then use map to return the square of each number
    let i = parseInt(int);
    return i * i;
  });
  
  return parseInt(array.join("")); // turn the array into a string and then a number
}


// Solution 3 
function squareDigits(num){
  let result = num
    .toString()                     // turn number to string
    .split("")                      // turn string into array
    .map( num => parseInt(num) )    // map each index and return a number, now you have a number array
    .map( num => num * num )        // map the number array and return the square of each number
    .join("")                       // turn the number array into a string
   
  return parseInt(result)           // turn the string into a number
}


// Solution 4 
const squareDigits = num => parseInt(num.toString().split("").map(num => parseInt(num)).map(num => num * num).join(""))


// Solution 5
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
function squareDigits (num) {
  let x = num.toString().split('').map(Number); 
  x.forEach((element, i) => x[i] = element * element);
  return Number(x.join(''));
}