Gatsby Node API Error Fix

In this tutorial, you'll learn about Gatsby Node API Error Fix. We cover key concepts, practical examples, and best practices.

The Problem

error Your site's "gatsby-node.js" is not exporting the "createPages" function.
Make sure it exports the "createPages" API via "exports.createPages = ..."

Gatsby does not find the expected Node API export in gatsby-<a href="/backend/nodejs/">node.js</a>.

Wrong

// gatsby-node.js
const createPages = ({ actions }) => {
  // create pages
}

Output: "gatsby-<a href="/backend/nodejs/">node.js</a>" is not exporting the "createPages" function.

The function is defined but not exported.

Right

exports.createPages = async ({ actions, graphql }) => {
  const { createPage } = actions

  const result = await graphql(`
    query {
      allMarkdownRemark {
        nodes {
          frontmatter { slug }
        }
      }
    }
  `)

  result.data.allMarkdownRemark.nodes.forEach(node => {
    createPage({
      path: node.frontmatter.slug,
      component: require.resolve('./src/templates/post.js'),
      context: { slug: node.frontmatter.slug },
    })
  })
}

Output: pages are created dynamically based on GraphQL query results.

Prevention

• Always use exports.createPages (or module.exports.createPages)
• Export all Node API functions explicitly
• Use exports.createPages for dynamic page creation and exports.onCreatePage for page modifications

Common Mistakes with node api

1. Using foldl instead of foldl' causing stack overflow on large lists
2. Forgetting deriving (Show, Eq) on custom data types needed for debugging
3. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable

These mistakes appear frequently in real-world GATSBY code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ