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Nest JS Pipe, Filters, Middleware and Exception Filters #03

https://www.youtube.com/watch?v=qJTVyI8H5mE

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Nest JS Pipe, Filters, Middleware and Exception Filters #03

NBB: Ad-hoc CLJS Scripting on Node.js

Nbb

Not babashka. Node.js babashka!?

Ad-hoc CLJS scripting on Node.js.

Status

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.

Requirements

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).

Usage

Install nbb from NPM:

$ npm install nbb -g

Omit -g for a local install.

Try out an expression:

$ nbb -e '(+ 1 2 3)'
6

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
"/private/tmp/test-script"
#js {:columns 216, :rows 47}
510
#js ["node_modules" "package-lock.json" "package.json" "script.cljs"]
#js [#js ["foo" "bar"]]
true
$ ls
node_modules
package-lock.json
package.json
script.cljs

Macros

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)
                                        body))))
            body
            binding-pairs)))

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 "https://clojure.org")
                                (.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 "https://clojure.org")
       _ (-> (.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)'
6
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.

Dependencies

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.

Classpath

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 [foo.bar :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"

Reagent

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

ink-demo.cljs:

(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]))

Promesa

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]
  (js/Promise.
   (fn [resolve _]
     (js/setTimeout resolve ms))))

(defn do-stuff
  []
  (p/do!
   (println "Doing stuff which takes a while")
   (sleep 1000)
   1))

(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
3

Also see API docs.

Js-interop

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.

Examples

See the examples directory for small examples.

Also check out these projects built with nbb:

API

See API documentation.

Migrating to shadow-cljs

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

Build

Prequisites:

  • babashka >= 0.4.0
  • Clojure CLI >= 1.10.3.933
  • 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: https://github.com/borkdude/nbb 
License: EPL-1.0

#node #javascript

Eva  Murphy

Eva Murphy

1625778000

Validatioin in Nest JS and DTO objects | Nest JS Node JS tutorials - 04

In this video, we are going to look at how to do validations of the request coming to the controller. Validating the request object is very important, and I will show you in this video how you can create a DTO and then define rules inside that DTO so that you can run validations.

Github code: https://my-lnk.com/r/2233233755

#nest js #node js #node #nest #javascript #dto

Eva  Murphy

Eva Murphy

1625770260

Introduction to Nest JS - A Node JS Framework - From The Basics

#nodejs #javascript

Let’s talk about Nest JS - a Node JS based progressive framework which comes with a lot of potentials.

It allows great modular code architecture and it comes with a lot of stuff already baked in so that you can start focusing on your idea without wasting too much time.

#nest js #node js #node #nest #javascript

Christa  Stehr

Christa Stehr

1597555560

Filtering an Array of Nested Objects Using Angular Pipes

Consider the below array of JSON objects exported from users.ts

//users.ts
export const users=[{
“name”:
{“title”:”Monsieur”,”first”:”Niklas”,”last”:”Philippe”},
“dob”:{“date”:”1973–02–17T18:35:33.898Z”,”age”:47},
“gender”:”male”,
“email”:”niklas.philippe@example.com”,
“location”:{“street”:{“number”:2179,”name”:”Avenue Joliot Curie”},”city”:”Aulnay-sous-Bois”,”state”:”Hautes-Pyrénées”,”country”:”France”,”postcode”:37752}
},
{
“name”:{“title”:”Mrs”,”first”:”Nicoline”,”last”:”Jensen”},
“dob”:{“date”:”1959–05–30T12:20:56.272Z”,”age”:61},
“gender”:”female”,”email”:”nicoline.jensen@example.com”,
“location”:{“street”:{“number”:544,”name”:”Poplar Dr”},”city”:”Australian Capital Territory”,”state”:”Queensland”,”country”:”Australia”,”postcode”:2703}
},
{
“name”:{“title”:”Miss”,”first”:”Lilly”,”last”:”Smith”},
“dob”:{“date”:”1995–04–11T08:12:02.912Z”,”age”:25},
“gender”:”female”,”email”:”lily.smith@example.com”,
“location”:{“street”:{“number”:8927,”name”:”Washington Ave”},”city”:”Cairns”,”state”:”Australian Capital Territory”,”country”:”Australia”,”postcode”:4313}
},
{
“name”:{“title”:”Mr”,”first”:”Julio”,”last”:”Ibanez”},
“dob”:{“date”:”1946–10–18T09:54:57.564Z”,”age”:74},
“gender”:”male”,”email”:”julio.ibanez@example.com”,
“location”:{“street”:{“number”:6283,”name”:”Calle de Atocha”},”city”:”Oviedo”,”state”:”Canarias”,”country”:”Spain”,”postcode”:94457}
},
{
“name”:{“title”:”Monsieur”,”first”:”Horst”,”last”:”Bernard”},
“dob”:{“date”:”1969–07–29T22:21:47.381Z”,”age”:51},
“gender”:”male”,”email”:”horst.bernard@example.com”,
“location”:{“street”:{“number”:1217,”name”:”Rue de Cuire”},”city”:”Nîmes”,”state”:”Maine-et-Loire”,”country”:”France”,”postcode”:27584}
},
]

As you can see that name, dob and location are properties that in turn have objects as values.

We shall a create a table with the above JSON data and search for any item in the table using Pipes.

Template:

<input type=”text” [(ngModel)]=”searchTerm” name=”searchTerm” placeholder=”Search”>

<table class=”table-bordered”>
<tr>
<th>Title</th>
<th>First Name</th>
<th>Last Name</th>
<th>Date</th>
<th>Age</th>
<th>Email</th>
<th>Street</th>
<th>City</th>
<th>State</th>
<th>Country</th>
<th>Postcode</th>
</tr>
<tr *ngFor=”let x of users|filter:searchTerm”>
<td>{{x.name.title}}</td>
<td>{{x.name.first}}</td>
<td>{{x.name.last}}</td>
<td>{{x.dob.date}}</td>
<td>{{x.dob.age}}</td>
<td>{{x.email}}</td>
<td>{{x.location.street.name}} {{x.location.street.number}}</td>
<td>{{x.location.city}}</td>
<td>{{x.location.state}}</td>
<td>{{x.location.country}}</td>
<td>{{x.location.postcode}}</td>
</tr>
</table>

As you can see, we have a textbox to enter the searchTerm and a table constructed with the JSON data.

**filter **is the selector of the **FilterPipe **which we shall implement to achieve the search functionality. We are passing 2 arguments to the pipe: The users array and the searchTerm entered in the textbox.

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#nested-objects #angular #closure #pipes #filter #searchterm

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