detect the active navigation anchor and style it

src/css/main.css

@@ -156,6 +156,11 @@ body,
   text-decoration: none;
 }
 
+.nav .nav__list .nav__item .nav__link.nav__link--active {
+  color: #FA3;
+  border-bottom: 2px solid #FA3;
+}
+
 .demo {
   margin-top: 40px;
 }

src/js/components/homagePage/NavBar.js

@@ -1,16 +1,60 @@
 import { createComponent } from '../../mini';
 
 export function NavBar() {
+  const removeActiveClassFromNonSelected = selected => {
+    const navLinks = document.querySelectorAll('.nav__link');
+    navLinks.forEach(link => {
+      if (link !== selected) {
+        link.classList.remove('nav__link--active');
+      }
+    });
+  };
+
+  // style the selected nav link at the first render
+  setImmediate(() => {
+    // if the url doesn't contain a hash, set the first nav link as active
+    if (!window.location.hash) {
+      window.location.hash = document.querySelector('.nav__link').getAttribute('href');
+    }
+
+    // style the initial selected nav link
+    const selected = document.querySelector(`a[href="${window.location.hash}"]`);
+    selected.classList.add('nav__link--active');
+  });
+
+  let storedHash = window.location.hash;
+  window.setInterval(() => {
+    if (window.location.hash !== storedHash) {
+      storedHash = window.location.hash;
+      if (storedHash === '#demo') {
+        const demoLink = document.querySelectorAll('.nav__link')[0];
+        demoLink.classList.add('nav__link--active');
+        removeActiveClassFromNonSelected(demoLink);
+      }
+      if (storedHash === '#select-game-language') {
+        const playLink = document.querySelectorAll('.nav__link')[1];
+        playLink.classList.add('nav__link--active');
+        removeActiveClassFromNonSelected(playLink);
+      }
+      if (storedHash === '#about') {
+        const aboutLink = document.querySelectorAll('.nav__link')[2];
+        aboutLink.classList.add('nav__link--active');
+        removeActiveClassFromNonSelected(aboutLink);
+      }
+    }
+    window.clearInterval();
+  }, 100);
+
   return createComponent({
     render() {
       return `
       <nav class="nav">
         <ul class="nav__list">
           <li class="nav__item">
-            <a href="#select-game-language" class="nav__link">Play</a>
+            <a href="#demo" class="nav__link">Demo</a>
           </li>
           <li class="nav__item">
-            <a href="#demo" class="nav__link">Demo</a>
+            <a href="#select-game-language" class="nav__link">Play</a>
           </li>
           <li class="nav__item">
             <a href="#about" class="nav__link">About</a>