fix web standards section arrow function

Author: yangdanny97

_includes/examples/dom.js

@@ -1,19 +1,19 @@
 // DOM API
 var clickMe = document.getElementById('click-me');
-clickMe.onclick = () => {
-  if (this.style.backgroundColor) {
-    this.style.backgroundColor = '';
-  } else {
-    this.style.backgroundColor = 'red';
-  }
+clickMe.onclick = function () {
+    if (this.style.backgroundColor) {
+        this.style.backgroundColor = '';
+    } else {
+        this.style.backgroundColor = 'red';
+    }
 }
 
 // D3 Selection API. Note: it attaches the
 // callbacks to each element in the selection
 d3.selectAll('.hover-me')
-  .on('mouseover', () => {
-    this.style.backgroundColor = 'yellow';
-  })
-  .on('mouseleave', () => {
-    this.style.backgroundColor = '';
-  });
+    .on('mouseover', function () {
+        this.style.backgroundColor = 'yellow';
+    })
+    .on('mouseleave', function () {
+        this.style.backgroundColor = '';
+    });

_includes/head.html

@@ -10,5 +10,5 @@
   <link rel="stylesheet" href="{{ "/css/syntax.css" | prepend: site.baseurl }}">
   <link rel="stylesheet" href="{{ "/css/graph.css" | prepend: site.baseurl }}">
 
-  <script type="text/javascript" src="{{ "/javascripts/d3.v4.min.js" | prepend: site.baseurl }}"></script>
+  <script type="text/javascript" src="{{ "/javascripts/d3.v5.min.js" | prepend: site.baseurl }}"></script>
 </head>

z01-web-standards.md

@@ -184,8 +184,8 @@ on the styling.
 
 <div class="example-row-2">
   <div class="example">
-    {% highlight html
-      %}{% include examples/svg2.svg %}
+    {% highlight html %}
+    {% include examples/svg2.svg %}
     {% endhighlight %}
   </div>