estoy usando un foro básico usando node.js y expreso escrito allí, y quiero cambiar a mongodb pero soy muy nuevo en esto. Ya he intentado algunos pasos, pero no va a ninguna parte. Solo quiero implementar mi base de datos de la misma manera que este código.

 var router = express.Router(); var fs = require('fs'); router.get('/forum',(req,res)=>{ res.render('forum',{db:req.app.locals.frm,'user':req.session.user}); }) .post('/forum',(req,res)=>{ var page = req.body; req.app.locals.frm.push({'category':page.cat,'subcategories':[]}); fs.writeFile('./forum-db.json',JSON.stringify(req.app.locals.frm),(e)=>{console.log(e);}); res.redirect('/forum'); }) .get('/del-elt/:pos',(req,res)=>{ var page = req.params; req.app.locals.frm.splice(page.pos,1); fs.writeFile('./forum-db.json',JSON.stringify(req.app.locals.frm),(e)=>{console.log(e);}); res.redirect('/forum'); }) .get('/category/:id',(req,res)=>{ var cat = req.app.locals.frm[req.params.id] res.render('category',{cat:cat,id:req.params.id,'user':req.session.user}) }) .post('/category',(req,res)=>{ var page = req.body; req.app.locals.frm[page.id].subcategories.push({'title':page.cat,'discussions':[]}); fs.writeFile('./forum-db.json',JSON.stringify(req.app.locals.frm),(e)=>{console.log(e);}); res.redirect('/category/'+page.id); }) .get('/del-cat/:id/:pos',(req,res)=>{ var page = req.params; req.app.locals.frm[page.id].subcategories.splice(page.pos,1); fs.writeFile('./forum-db.json',JSON.stringify(req.app.locals.frm),(e)=>{console.log(e);}); res.redirect('/category/'+page.id); }) .get('/discussion/:cat/:id',(req,res)=>{ var dis = req.app.locals.frm[req.params.cat].subcategories[req.params.id]; res.render('discussion',{dis:dis,cat:req.params.cat,id:req.params.id,'user':req.session.user}) }) .post('/discussion',(req,res)=>{ var page = req.body; var user = req.session.user; var d = new Date(); var date = d.getDate()+"/"+d.getMonth()+"/"+d.getFullYear()+" ("+d.getHours()+":"+d.getMinutes()+")"; req.app.locals.frm[page.cat].subcategories[page.id].discussions.push([ page.message,user.mail,date ]); //+mail+date fs.writeFile('./forum-db.json',JSON.stringify(req.app.locals.frm),(e)=>{console.log(e);}); res.redirect('/discussion/'+page.cat+'/'+page.id); }) .get('/del-dis/:cat/:id/:pos',(req,res)=>{ var page = req.params; req.app.locals.frm[page.cat].subcategories[page.id].discussions.splice(page.pos,1); fs.writeFile('./forum-db.json',JSON.stringify(req.app.locals.frm),(e)=>{console.log(e);}); res.redirect('/discussion/'+page.cat+'/'+page.id); });

Si alguien tiene alguna pista de como hacerlo. Gracias