Change color of selected tab and fix js

canvas.js

@@ -69,11 +69,19 @@ let draw = function() {
 }
 
 let bgColorElems = document.querySelectorAll('.colorpicker input[type="radio"], #step3 input[type="radio"]');
-let i;
-
-for (i in bgColorElems) {
+for (let i = 0; i < bgColorElems.length; ++i) {
   bgColorElems[i].onchange = draw;
 }
 document.getElementById('step2value').oninput = draw;
 document.getElementById('signature').oninput = draw;
 window.onload = draw;
+
+let navElems = document.querySelectorAll('nav > a');
+for (let i = 0; i < navElems.length; ++i) {
+  navElems[i].onclick = function(e) {
+    for (let j = 0; j < navElems.length; ++j) {
+      navElems[j].classList.remove('active-tab');
+    }
+    e.target.classList.add('active-tab');
+  }
+}

style.css

@@ -30,6 +30,10 @@ nav > * {
   border-bottom: 1px solid #3b68b0;
 }
 
+nav > .active-tab {
+  background-color: #3b68b0;
+}
+
 a {
   text-decoration: none;
   color: white;