gatsby-node.js: make onCreateNode more readable

gatsby-node.js

@@ -49,16 +49,25 @@ exports.createPages = ({ graphql, boundActionCreators }) => {
 // Add custom slug for blog posts to both File and MarkdownRemark nodes.
 exports.onCreateNode = ({ node, boundActionCreators, getNode }) => {
   const { createNodeField } = boundActionCreators
-  if (node.internal.type === `File`) {
+
+  switch (node.internal.type) {
+    case 'File':
       const parsedFilePath = path.parse(node.relativePath)
       const slug = `/${parsedFilePath.dir}/`
-    createNodeField({ node, fieldName: `slug`, fieldValue: slug })
-  } else if (node.internal.type === `MarkdownRemark`) {
+      createNodeField({
+        node,
+        fieldName: 'slug',
+        fieldValue: slug
+      })
+      return
+
+    case 'MarkdownRemark':
       const fileNode = getNode(node.parent)
       createNodeField({
         node,
-      fieldName: `slug`,
+        fieldName: 'slug',
         fieldValue: fileNode.fields.slug,
       })
+      return
   }
 }