model.js

'use strict'

module.exports = {
    bicycle: bicycleModel()
}

function bicycleModel() {
    const db = {
        1: { brand: 'Veloretti', color: 'green' },
        2: { brand: 'Batavus', color: 'yellow' }
    }

    return {
        create, read, update, del, uid
    }

    function uid() {
        return Object.keys(db)
            .sort((a, b) => a - b)
            .map(Number)
            .filter((n) => !isNaN(n))
            .pop() + 1 + ''
    }

    function create(id, data, cb) {
        if (db.hasOwnProperty(id)) {
            const err = Error('resource exists')
            setImmediate(() => cb(err))
            return
        }
        db[id] = data
        setImmediate(() => cb(null, id))
    }

    function read(id, cb) {
        if (!(db.hasOwnProperty(id))) {
            const err = Error('not found')
            setImmediate(() => cb(err))
            return
        }
        setImmediate(() => cb(null, db[id]))
    }

    function update(id, data, cb) {
        if (!(db.hasOwnProperty(id))) {
            const err = Error('not found')
            setImmediate(() => cb(err))
            return
        }
        db[id] = data
        setImmediate(() => cb())
    }

    function del(id, cb) {
        if (!(db.hasOwnProperty(id))) {
            const err = Error('not found')
            setImmediate(() => cb(err))
            return
        }
        delete db[id]
        setImmediate(() => cb())
    }
}