Expand stub for "Creating slugs for pages" page

docs/docs/creating-slugs-for-pages.md

@@ -2,7 +2,48 @@
 title: Creating slugs for pages
 ---
 
-This is a stub. Help our community expand it.
+The logic for creating slugs from file names can get tricky, the `gatsby-source-filesystem` plugin ships with a function for creating them.
 
-Please use the [Gatsby Style Guide](/docs/gatsby-style-guide/) to ensure your
-pull request gets accepted.
+## Install
+
+`npm install --save gatsby-source-filesystem`
+
+## Create slugs in gatsby-node.js
+
+Add your new slugs directly onto the `MarkdownRemark` nodes. Any data you add to nodes is available to query later with GraphQL.
+
+To do so, you'll use a function passed to our API implementation called [`createNodeField`](/docs/bound-action-creators/#createNodeField). This function allows you to create additional fields on nodes created by other plugins.
+
+```javascript{3,4,6-11}:title=gatsby-node.js
+const { createFilePath } = require(`gatsby-source-filesystem`)
+
+exports.onCreateNode = ({ node, getNode, actions }) => {
+ const { createNodeField } = actions
+ if (node.internal.type === `MarkdownRemark`) {
+ const slug = createFilePath({ node, getNode, basePath: `pages` })
+ createNodeField({
+ node,
+ name: `slug`,
+ value: slug,
+ })
+ }
+}
+```
+
+## Query created slugs
+
+Open refresh Graph_i_QL, then run this GraphQL query to see all your slugs:
+
+```graphql
+{
+ allMarkdownRemark {
+ edges {
+ node {
+ fields {
+ slug
+ }
+ }
+ }
+ }
+}
+```