Create 004.js

004.js

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+/*
+Source: https://projecteuler.net/problem=4
+Problem:
+"A palindromic number reads the same both ways. 
+The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
+
+Find the largest palindrome made from the product of two 3-digit numbers."
+
+My Algorithm in words:
+1. Define a function to check if a string is a palindrome
+2. Define a variable to hold the largest palindromic product so far
+3. Loop through all combinations of 3 digit numbers (100-999) x (100-999)
+4. If the product is greater than the variable that holds the largest palindromic product so far, update the variable
+5. Return the variable at the end, and we have the solution!
+*/
+
+function isPalindrome(string) {
+	if (string === string.split("").reverse().join("")) { //compare the string with a reversed version of itself
+  	return true; //if it's the same, then the string is a palindrome
+  } else {
+  	return false;
+  }
+}
+
+function solution() {
+  var largestPalindromeSoFar = 0;
+
+	for (let i = 100; i <= 999; i++) { //first number is from 100 - 999
+  	for (let j = i; j <= 999; j++) { //second number is from (first number) - 999 to avoid multiplying the same numbers in reverse order (a * b = b * a) because it's a waste of time/computer resources
+    	if (isPalindrome((i*j).toString())) { //if it's a palindrome,
+        if ((i*j) > largestPalindromeSoFar) { //and greater than the largest palindrome so far,
+          largestPalindromeSoFar = i*j; //update the value of largestPalindromeSoFar
+        }
+      }
+    }
+  }
+
+  return largestPalindromeSoFar; //once the loop is done, return the answer!
+}
+
+console.log(solution()); //outputs the answer!