Next.js on the server-side— notes to self

This is a curation of Next.js documentation, explanations, and advice. With a few code snippets and images to help along the way.

It focusses mainly on how the ‘server-side’ works in Next.js. Spoiler — it can do more than just render HTML

Currently, Next.js latest version is 9.5.

What is Next.js?

It’s a framework for building server-side rendered React applications.

But Next.js is not just for building an application’s frontend, because of its ‘server-side’, it can be used to build a full backend for the application as well.

How does the server-side work?

The ‘server-side’ in Next.js applications can be separated into two parts:

  1. The server-side rendering — how Next.js generates HTML on the server-side and sends it to the client
  2. The backend server — how Next.js supports a backend server and APIs

The server-side rendering (pre-rendering)

Pre-rendering = general term for rendering HTML before it is sent to the client

By default, Next.js will pre-render every page, but can do so in two different ways:

  1. Static generation
  2. Server-side rendering (SSR)

An application can use a combination of these methods, where the method used for a given page is determined by the page’s data requirements — see the ‘data fetching on the server-side’ section below for more details.

**Static generation **means that the HTML is generated once on the server at build-time, and this HTML is reused for each client request.

This is the recommended approach for performance reasons (better caching), however, it comes with some obvious limitations when it comes to fetching data for that page — the data can only be fetched during the application’s build process using the getStaticProps method.

This might be acceptable when the data being fetched does not change often, and/or in scenarios where the user does not always need the most updated data. But often it is crucial that the user is shown a current view of the data, meaning that static generation of pages cannot be used.

**Server-side rendering (SSR) **means that the HTML is generated on the server on each request for the page — the HTML is ‘dynamic’ rather than ‘static’ as it will depend on the data required.

#react #nextjs #server-side-rendering #javascript #javascript-tips

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Next.js on the  server-side— notes to self

NBB: Ad-hoc CLJS Scripting on Node.js


Not babashka. Node.js babashka!?

Ad-hoc CLJS scripting on Node.js.


Experimental. Please report issues here.

Goals and features

Nbb's main goal is to make it easy to get started with ad hoc CLJS scripting on Node.js.

Additional goals and features are:

  • Fast startup without relying on a custom version of Node.js.
  • Small artifact (current size is around 1.2MB).
  • First class macros.
  • Support building small TUI apps using Reagent.
  • Complement babashka with libraries from the Node.js ecosystem.


Nbb requires Node.js v12 or newer.

How does this tool work?

CLJS code is evaluated through SCI, the same interpreter that powers babashka. Because SCI works with advanced compilation, the bundle size, especially when combined with other dependencies, is smaller than what you get with self-hosted CLJS. That makes startup faster. The trade-off is that execution is less performant and that only a subset of CLJS is available (e.g. no deftype, yet).


Install nbb from NPM:

$ npm install nbb -g

Omit -g for a local install.

Try out an expression:

$ nbb -e '(+ 1 2 3)'

And then install some other NPM libraries to use in the script. E.g.:

$ npm install csv-parse shelljs zx

Create a script which uses the NPM libraries:

(ns script
  (:require ["csv-parse/lib/sync$default" :as csv-parse]
            ["fs" :as fs]
            ["path" :as path]
            ["shelljs$default" :as sh]
            ["term-size$default" :as term-size]
            ["zx$default" :as zx]
            ["zx$fs" :as zxfs]
            [nbb.core :refer [*file*]]))

(prn (path/resolve "."))

(prn (term-size))

(println (count (str (fs/readFileSync *file*))))

(prn (sh/ls "."))

(prn (csv-parse "foo,bar"))

(prn (zxfs/existsSync *file*))

(zx/$ #js ["ls"])

Call the script:

$ nbb script.cljs
#js {:columns 216, :rows 47}
#js ["node_modules" "package-lock.json" "package.json" "script.cljs"]
#js [#js ["foo" "bar"]]
$ ls


Nbb has first class support for macros: you can define them right inside your .cljs file, like you are used to from JVM Clojure. Consider the plet macro to make working with promises more palatable:

(defmacro plet
  [bindings & body]
  (let [binding-pairs (reverse (partition 2 bindings))
        body (cons 'do body)]
    (reduce (fn [body [sym expr]]
              (let [expr (list '.resolve 'js/Promise expr)]
                (list '.then expr (list 'clojure.core/fn (vector sym)

Using this macro we can look async code more like sync code. Consider this puppeteer example:

(-> (.launch puppeteer)
      (.then (fn [browser]
               (-> (.newPage browser)
                   (.then (fn [page]
                            (-> (.goto page "")
                                (.then #(.screenshot page #js{:path "screenshot.png"}))
                                (.catch #(js/console.log %))
                                (.then #(.close browser)))))))))

Using plet this becomes:

(plet [browser (.launch puppeteer)
       page (.newPage browser)
       _ (.goto page "")
       _ (-> (.screenshot page #js{:path "screenshot.png"})
             (.catch #(js/console.log %)))]
      (.close browser))

See the puppeteer example for the full code.

Since v0.0.36, nbb includes promesa which is a library to deal with promises. The above plet macro is similar to promesa.core/let.

Startup time

$ time nbb -e '(+ 1 2 3)'
nbb -e '(+ 1 2 3)'   0.17s  user 0.02s system 109% cpu 0.168 total

The baseline startup time for a script is about 170ms seconds on my laptop. When invoked via npx this adds another 300ms or so, so for faster startup, either use a globally installed nbb or use $(npm bin)/nbb script.cljs to bypass npx.


NPM dependencies

Nbb does not depend on any NPM dependencies. All NPM libraries loaded by a script are resolved relative to that script. When using the Reagent module, React is resolved in the same way as any other NPM library.


To load .cljs files from local paths or dependencies, you can use the --classpath argument. The current dir is added to the classpath automatically. So if there is a file foo/bar.cljs relative to your current dir, then you can load it via (:require [ :as fb]). Note that nbb uses the same naming conventions for namespaces and directories as other Clojure tools: foo-bar in the namespace name becomes foo_bar in the directory name.

To load dependencies from the Clojure ecosystem, you can use the Clojure CLI or babashka to download them and produce a classpath:

$ classpath="$(clojure -A:nbb -Spath -Sdeps '{:aliases {:nbb {:replace-deps {com.github.seancorfield/honeysql {:git/tag "v2.0.0-rc5" :git/sha "01c3a55"}}}}}')"

and then feed it to the --classpath argument:

$ nbb --classpath "$classpath" -e "(require '[honey.sql :as sql]) (sql/format {:select :foo :from :bar :where [:= :baz 2]})"
["SELECT foo FROM bar WHERE baz = ?" 2]

Currently nbb only reads from directories, not jar files, so you are encouraged to use git libs. Support for .jar files will be added later.

Current file

The name of the file that is currently being executed is available via nbb.core/*file* or on the metadata of vars:

(ns foo
  (:require [nbb.core :refer [*file*]]))

(prn *file*) ;; "/private/tmp/foo.cljs"

(defn f [])
(prn (:file (meta #'f))) ;; "/private/tmp/foo.cljs"


Nbb includes reagent.core which will be lazily loaded when required. You can use this together with ink to create a TUI application:

$ npm install ink


(ns ink-demo
  (:require ["ink" :refer [render Text]]
            [reagent.core :as r]))

(defonce state (r/atom 0))

(doseq [n (range 1 11)]
  (js/setTimeout #(swap! state inc) (* n 500)))

(defn hello []
  [:> Text {:color "green"} "Hello, world! " @state])

(render (r/as-element [hello]))


Working with callbacks and promises can become tedious. Since nbb v0.0.36 the promesa.core namespace is included with the let and do! macros. An example:

(ns prom
  (:require [promesa.core :as p]))

(defn sleep [ms]
   (fn [resolve _]
     (js/setTimeout resolve ms))))

(defn do-stuff
   (println "Doing stuff which takes a while")
   (sleep 1000)

(p/let [a (do-stuff)
        b (inc a)
        c (do-stuff)
        d (+ b c)]
  (prn d))
$ nbb prom.cljs
Doing stuff which takes a while
Doing stuff which takes a while

Also see API docs.


Since nbb v0.0.75 applied-science/js-interop is available:

(ns example
  (:require [applied-science.js-interop :as j]))

(def o (j/lit {:a 1 :b 2 :c {:d 1}}))

(prn (j/select-keys o [:a :b])) ;; #js {:a 1, :b 2}
(prn (j/get-in o [:c :d])) ;; 1

Most of this library is supported in nbb, except the following:

  • destructuring using :syms
  • property access using .-x notation. In nbb, you must use keywords.

See the example of what is currently supported.


See the examples directory for small examples.

Also check out these projects built with nbb:


See API documentation.

Migrating to shadow-cljs

See this gist on how to convert an nbb script or project to shadow-cljs.



  • babashka >= 0.4.0
  • Clojure CLI >=
  • Node.js 16.5.0 (lower version may work, but this is the one I used to build)

To build:

  • Clone and cd into this repo
  • bb release

Run bb tasks for more project-related tasks.

Download Details:
Author: borkdude
Download Link: Download The Source Code
Official Website: 
License: EPL-1.0

#node #javascript

Eva  Murphy

Eva Murphy


Google analytics Setup with Next JS, React JS using Router Events - 14

In this video, we are going to implement Google Analytics to our Next JS application. Tracking page views of an application is very important.

Google analytics will allow us to track analytics information.

App link:

You can find me on:

#next js #js #react js #react #next #google analytics

Eldora  Bradtke

Eldora Bradtke


How to Generate Server-Side PDF Reports With Puppeteer, D3 & Handlebars

Looking for a way to create a design-heavy, data-driven, beautifully styled PDF report—server-side with similar tools to what you are already using on the front-end? Stop your Google search. You’ve come to the right place. I was in the same boat as you a few months ago while helping a client with this exact problem. In order to accomplish this feat, I developed a four-step solution using Puppeteer, D3, and handlebars. In this post, I’ll give you step by step instructions on creating server-side pdf reports. Let’s dive in.

An example of a PDF page generated using this method.

An example of a PDF page generated using this method.

In this post, we’ll cover:

  • Setting up Puppeteer and Handlebars
  • Creating a generator to make our PDF
  • Building out a handlebars template
  • Adding the finishing touches

The CHallenges of Creating These PDF Reports:

Because we’re using a template framework to access standard web technologies along with Puppeteer to manage the PDF, we’ll need to think about these things during development:

  • Pages will manually need to be constrained.
  • We won’t have access to CSS media props other than “screen.” (no “page-break-after” or the print media type)
  • We won’t be able to use dev tools to debug irregularities once the PDF is compiled and rendered.
  • Puppeteer itself adds extra build time and size to your deployments.
  • Generating a report can take a while depending on file size.

For this example, let’s assume we already have the base of our project up and running Node/Express, and some type of ORM and DB solutions. We’re all set to feed our sweet, sweet data into a report.

The Tools We Need to Make This Happen


HTML templating framework from the Mustache family. This allows for Partial templating (fancy talk for components) and custom and built-in helper functionality to expand on our logic.

npm install handlebars

Example using partials and built-in blocks

{{#each poleComparison as |page|}}
<div class="page">
  {{#each page.pairs as |polePair|}}
    {{> comparison-header polePair=polePair }}
        <div class="comparison-tables">
            {{> comparison-body polePair=polePair }}
  {{> footer @root }}


A node library that will provide us access to a chrome headless instance for generating the PDF based on our compiled Handlebars templates.

npm install puppeteer

A list of use cases:

  • Generate screenshots and PDFs of pages.
  • Crawl a SPA (Single-Page Application) and generate pre-rendered content (i.e. “SSR” (Server-Side Rendering)).
  • Create an up-to-date, automated testing environment.
  • Test Chrome Extensions.

D3 (Data-Driven Documents)

D3.js is a JavaScript library for manipulating documents based on data. D3 helps you bring data to life using HTML, SVG, and CSS. D3’s emphasis on web standards gives you the full capabilities of modern browsers without tying yourself to a proprietary framework, combining powerful visualization components and a data-driven approach to DOM manipulation.

<script src=""></script> 

#javascript #server-side #d3.js #js #handlebars #puppeteer #server-side development

Eva  Murphy

Eva Murphy


Next JS Handling Email Verification token on Server Side in Next js To Check Token - 18

In this video, I am going to show you the code behind verifying the token that a user will get on his/her email. We will be looking at the feature of doing server-side API calls inside Next JS to verify the token from the dynamic URL that we have created. Once the token is verified, we will automatically log in the user and take his/her to the dashboard.

App link:

You can find me on:

#next js #token #next #email

Eva  Murphy

Eva Murphy


Laravel API and React Next JS frontend development - 28

In this video, I wanted to touch upon the functionality of adding Chapters inside a Course. The idea was to not think much and start the development and pick up things as they come.

There are places where I get stuck and trying to find answers to it up doing what every developer does - Google and get help. I hope this will help you understand the flow and also how developers debug while doing development.

App url:
Github code links below:
Next JS App:
Laravel API:

You can find me on:

#next js #api #react next js #next #frontend #development