gatsby-node.js

const fs = require('fs');
const path = require('path');
const dirPath = path.join(__dirname + '/data/')

//helpers
//reads all json files

const readFiles = (dir) => {
    const returnFiles = [];

    fs.readdir(dir, (err, files) => {
        if(err) {
            console.log(`unable to scan`, err)
        }
        files.forEach((file) => {
            fs.readFile(dir+file, 'utf-8', (err, contents) => {
                if(err) console.log(err);
                
            });
        })
    })
    if(!returnFiles) throw e
    return returnFiles
}

//jsonify data
const jsonifyDataFiles = (filename) => {
    return JSON.parse(filename, 'utf-8');
}

//create contentnodes
const createContents = (contents) => {
    try {
        if(!Array.isArray(contents) || contents.length < 1) 
        { 
            return
        }
    else {
        const contentsResult = new Array();
        contents.map( content => {
            contentsResult.push(content)
        })
        return contentsResult
        }
    } catch(e) {
        console.log('We can not creatContents() here. check contents for beeing Array and length >= 1')
    }
}


exports.createPages = ({actions: { createPage }}) => {

   const files = readFiles(dirPath)


   //we can not iterate over this, since its not here yet,
   //gatsby lifecycle?
   
    files.forEach(file => {
        const jsonPage = jsonifyDataFiles(file);
        if(!jsonPage) console.log('err');
        console.log('see',jsonPage)
        if(jsonPage.type === 'index') {
            console.log('creating index pages');
            createPage({
                path: `/${jsonPage.pageTitle}`,
                component : require.resolve('./src/temaplates/indexPage.js')
            })
        }
        if(jsonPage.type === 'content') {
            console.log('creating chapter pages');
            jsonPage.chapters.forEach(chapter => {
                createPage({
                path : `/${jsonPage.pageTitle}/${chapter.slug}`,
                component : require.resolve('./src/templates/page.js'),
                context : {
                    title: chapter.chapterTitle,
                    contents: createContents(chapter.contents)
                    }
                })
            });
        }
    })
}