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1623378921

Nest JS Advance Course #01

https://www.youtube.com/watch?v=i1wN86rnMEI&t=7s

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Nest JS Advance Course #01
JavaScript Daily

JavaScript Daily

1632537859

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

Ananya Gupta

Ananya Gupta

1604922206

Top 7 Advantages Of Advanced Excel Learning

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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

Ananya Gupta

Ananya Gupta

1608615386

Top Reasons To Choose ReactJS

The principal concept at the back of ReactJS improvement become to discover a framework that allows in constructing a dynamic library with excessive performance. An appropriate instance of this becomes to offer newsfeeds on equal time whilst human beings are chatting. Optimization of the improvement technique and bringing on JavaScript become all that become required at that time. ReactJS is greater like an open-supply JavaScript library in place of a framework. Used for constructing superb consumer interfaces, it is ideal for rendering performance.

Reasons to pick out React.js/React/ReactJS

Out of the several reasons React.JS can be future of hybrid mobile app, some of the interesting ones are:

  • React’s virtual DOM is faster as it only refreshes a part of the page, rather than the conventional full refresh model
  • Easy to create UI Test Cases
  • Easy to reuse the code components
  • It can display components in large amounts quickly and efficiently
  • Specialized chrome extension makes it easy to debug
  • Any data changes require manual processing
  • It is view oriented
  • It’s one of the top JavaScript frameworks among ReactJS developers and is growing
  • Rendering the code from the server to browser will eventually improve the SEO of the webpage
  • It improves debugging speed, making it easier for developers
  • It covers both iOS and Android
  • As it makes use of reusable components, it becomes easy for the hybrid applications to render natively
  • React Native UI components can be applied without re-writing to an existing app’s code
  • It provides support for both front-end and server-side

Cons of ReactJS Making use of JSX which permits blending HTML with JavaScript is taken into consideration a critical drawback through ReactJS builders as it’s far complicated and has a steep mastering curve. Join ReactJS Online Training and learn the regular launch of the latest tools, documentation nonetheless stays incomplete, which makes it tough for brand spanking new ReactJS builders to apprehend and code. With the excessive tempo of improvement, ReactJS builders have to quickly research new methods of improvement. With rapid evolution, now no longer each developer is capable of preserve tempo. What’s our tackle it?

AngularJS is a featured framework at the same time as ReactJS is a library. You will need to write much less code with ReactJS and it even plays higher because of the implementation of digital DOM. As React has simply commenced its network is developing. Node.js is a JavaScript runtime that is rapid and lightweight. It may be used to create rapid and scalable networking packages. With Client-Side statistics rendering and a top configuration, ReactJS is an outright desire of JavaScript framework Developers.

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Sival Alethea

Sival Alethea

1624291630

Data Structures Easy to Advanced Course - Full Tutorial from a Google Engineer

Learn and master the most common data structures in this full course from Google engineer William Fiset. This course teaches data structures to beginners using high quality animations to represent the data structures visually.

You will learn how to code various data structures together with simple to follow step-by-step instructions. Every data structure presented will be accompanied by some working source code (in Java) to solidify your understanding.
⭐️ Course Contents ⭐️
⌨️ (0:00:00) Abstract data types
⌨️ (0:04:28) Introduction to Big-O
⌨️ (0:17:00) Dynamic and Static Arrays
⌨️ (0:27:40) Dynamic Array Code
⌨️ (0:35:03) Linked Lists Introduction
⌨️ (0:49:16) Doubly Linked List Code
⌨️ (0:58:26) Stack Introduction
⌨️ (1:09:40) Stack Implementation
⌨️ (1:12:49) Stack Code
⌨️ (1:15:58) Queue Introduction
⌨️ (1:22:03) Queue Implementation
⌨️ (1:27:26) Queue Code
⌨️ (1:31:32) Priority Queue Introduction
⌨️ (1:44:16) Priority Queue Min Heaps and Max Heaps
⌨️ (1:49:55) Priority Queue Inserting Elements
⌨️ (1:59:27) Priority Queue Removing Elements
⌨️ (2:13:00) Priority Queue Code
⌨️ (2:28:26) Union Find Introduction
⌨️ (2:33:57) Union Find Kruskal’s Algorithm
⌨️ (2:40:04) Union Find - Union and Find Operations
⌨️ (2:50:30) Union Find Path Compression
⌨️ (2:56:37) Union Find Code
⌨️ (3:03:54) Binary Search Tree Introduction
⌨️ (3:15:57) Binary Search Tree Insertion
⌨️ (3:21:20) Binary Search Tree Removal
⌨️ (3:34:47) Binary Search Tree Traversals
⌨️ (3:46:17) Binary Search Tree Code
⌨️ (3:59:26) Hash table hash function
⌨️ (4:16:25) Hash table separate chaining
⌨️ (4:24:10) Hash table separate chaining source code
⌨️ (4:35:44) Hash table open addressing
⌨️ (4:46:36) Hash table linear probing
⌨️ (5:00:21) Hash table quadratic probing
⌨️ (5:09:32) Hash table double hashing
⌨️ (5:23:56) Hash table open addressing removing
⌨️ (5:31:02) Hash table open addressing code
⌨️ (5:45:36) Fenwick Tree range queries
⌨️ (5:58:46) Fenwick Tree point updates
⌨️ (6:03:09) Fenwick Tree construction
⌨️ (6:09:21) Fenwick tree source code
⌨️ (6:14:47) Suffix Array introduction
⌨️ (6:17:54) Longest Common Prefix (LCP) array
⌨️ (6:21:07) Suffix array finding unique substrings
⌨️ (6:25:36) Longest common substring problem suffix array
⌨️ (6:37:04) Longest common substring problem suffix array part 2
⌨️ (6:43:41) Longest Repeated Substring suffix array
⌨️ (6:48:13) Balanced binary search tree rotations
⌨️ (6:56:43) AVL tree insertion
⌨️ (7:05:42) AVL tree removals
⌨️ (7:14:12) AVL tree source code
⌨️ (7:30:49) Indexed Priority Queue | Data Structure
⌨️ (7:55:10) Indexed Priority Queue | Data Structure | Source Code

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