Create custom exponent method

bot/controllers/verify.js

@@ -7,13 +7,21 @@ const nodemailer = require('nodemailer');
 // Modified to fit style guide from this SO answer:
 // https://stackoverflow.com/a/39774334
 const generateCode = (n) => {
+  // Workaround method for Math.pow() and ** operator
+  const pow = (base, exp) => {
+    let result = 1;
+    for (let i = 0; i < exp; i += 1) {
+      result *= base;
+    }
+    return result;
+  };
   const add = 1;
   let max = 12 - add;
   let min = 0;
   if (n > max) {
     return generateCode(max) + generateCode(n - max);
   }
-  max = 10000000;
+  max = pow(10, n + add);
   min = max / 10;
   const number = Math.floor(Math.random() * (max - (min + 1))) + min;
   return ('' + number).substring(add);