populated the JS file. Implemented Node.js and added comments for clarity

Author: marleomac3

lesson_04/ljmcwilliams/findPrimeNum.js

@@ -0,0 +1,21 @@
+const readline = require('readline'); //"require()" imports the readline module which will process the user input
+const read = readline.createInterface({
+    input: process.stdin, //this acts as an input scanner
+    output: process.stdout //this works like a normal console.log combined with a user's input
+});
+let isConditionMet = false;
+
+/* When looking at the Node.js docs, it states '.question()' displays the query (in this case the user prompt).
+It waits for an input and uses it as the first argument in a callback function (here I am using a arrow function). */
+read.question("Enter a number: ", (answer) => {
+    for (let i = 2; i < answer; i++) {
+            if ((answer / i) == parseInt(answer / i)) { //similar to the "(int)" statement in java, parseInt converts doubles to ints
+                console.log(answer + " is not a prime number.");
+                isConditionMet = true;
+                read.close(); //this works similar to a break statement in java and ends the program
+            }
+        } if (!isConditionMet) {
+            console.log(answer + " is a prime number.");
+            read.close();
+        }
+})