Node-Cron | A Simple Task Scheduler for Node.js

Cron is a tool that allows you to execute something on a schedule. This is typically done using the cron syntax. We allow you to execute a function whenever your scheduled job triggers. We also allow you to execute a job external to the javascript process using child_process. Additionally, this library goes beyond the basic cron syntax and allows you to supply a Date object. This will be used as the trigger for your callback. Cron syntax is still an acceptable CronTime format. Although the Cron patterns supported here extend on the standard Unix format to support seconds digits, leaving it off will default to 0 and match the Unix behavior.

Installation

npm install cron

If You Are Submitting Bugs/Issues

Because we can't magically know what you are doing to expose an issue, it is best if you provide a snippet of code. This snippet need not include your secret sauce, but it must replicate the issue you are describing. The issues that get closed without resolution tend to be the ones without code examples. Thanks.

Versions and Backwards compatibility breaks:

As goes with semver, breaking backwards compatibility should be explicit in the versioning of your library. As such, we'll upgrade the version of this module in accordance with breaking changes (I'm not always great about doing it this way so if you notice that there are breaking changes that haven't been bumped appropriately please let me know).

Usage (basic cron usage):

var CronJob = require('cron').CronJob;
var job = new CronJob(
    '* * * * * *',
    function() {
        console.log('You will see this message every second');
    },
    null,
    true,
    'America/Los_Angeles'
);
// Use this if the 4th param is default value(false)
// job.start()

Note - You don't need to explicitly start a job in order to make it run since the 4th parameter is set to true. However, by default you need to call job.start() to start the cron job, which gives a little more control over running your jobs.

There are more examples available in this repository at: /examples

Available Cron patterns:

Asterisk. E.g. *
Ranges. E.g. 1-3,5
Steps. E.g. */2

Read up on cron patterns here. Note the examples in the link have five fields, and 1 minute as the finest granularity, but this library has six fields, with 1 second as the finest granularity.

There are tools that help when constructing your cronjobs. You might find something like https://crontab.guru/ or https://cronjob.xyz/ helpful. But, note that these don't necessarily accept the exact same syntax as this library, for instance, it doesn't accept the seconds field, so keep that in mind.

Cron Ranges

When specifying your cron values you'll need to make sure that your values fall within the ranges. For instance, some cron's use a 0-7 range for the day of week where both 0 and 7 represent Sunday. We do not. And that is an optimisation.

  • Seconds: 0-59
  • Minutes: 0-59
  • Hours: 0-23
  • Day of Month: 1-31
  • Months: 0-11 (Jan-Dec)
  • Day of Week: 0-6 (Sun-Sat)

Gotchas

  • Millisecond level granularity in JS or moment date objects. Because computers take time to do things, there may be some delay in execution. This should be on the order of milliseconds. This module doesn't allow MS level granularity for the regular cron syntax, but does allow you to specify a real date of execution in either a javascript date object or a moment object. When this happens you may find that you aren't able to execute a job that should run in the future like with new Date().setMilliseconds(new Date().getMilliseconds() + 1). This is due to those cycles of execution above. This wont be the same for everyone because of compute speed. When I tried it locally I saw that somewhere around the 4-5 ms mark was where I got consistent ticks using real dates, but anything less than that would result in an exception. This could be really confusing. We could restrict the granularity for all dates to seconds, but felt that it wasn't a huge problem so long as you were made aware. If this becomes more of an issue, We can revisit it.
  • Arrow Functions for onTick Arrow functions get their this context from their parent scope. Thus, if you use them, you will not get the this context of the cronjob. You can read a little more in this ticket GH-40

API

Parameter Based

  • job - shortcut to new cron.CronJob().
  • time - shortcut to new cron.CronTime().
  • sendAt - tells you when a CronTime will be run.
  • timeout - tells you when the next timeout is.
  • CronJob
    • constructor(cronTime, onTick, onComplete, start, timezone, context, runOnInit, utcOffset, unrefTimeout) - Of note, the first parameter here can be a JSON object that has the below names and associated types (see examples above).
      • cronTime - [REQUIRED] - The time to fire off your job. This can be in the form of cron syntax or a JS Date object.
      • onTick - [REQUIRED] - The function to fire at the specified time. If an onComplete callback was provided, onTick will receive it as an argument. onTick may call onComplete when it has finished its work.
      • onComplete - [OPTIONAL] - A function that will fire when the job is stopped with job.stop(), and may also be called by onTick at the end of each run.
      • start - [OPTIONAL] - Specifies whether to start the job just before exiting the constructor. By default this is set to false. If left at default you will need to call job.start() in order to start the job (assuming job is the variable you set the cronjob to). This does not immediately fire your onTick function, it just gives you more control over the behavior of your jobs.
      • timeZone - [OPTIONAL] - Specify the timezone for the execution. This will modify the actual time relative to your timezone. If the timezone is invalid, an error is thrown. You can check all timezones available at Moment Timezone Website. Probably don't use both timeZone and utcOffset together or weird things may happen.
      • context - [OPTIONAL] - The context within which to execute the onTick method. This defaults to the cronjob itself allowing you to call this.stop(). However, if you change this you'll have access to the functions and values within your context object.
      • runOnInit - [OPTIONAL] - This will immediately fire your onTick function as soon as the requisite initialization has happened. This option is set to false by default for backwards compatibility.
      • utcOffset - [OPTIONAL] - This allows you to specify the offset of your timezone rather than using the timeZone param. Probably don't use both timeZone and utcOffset together or weird things may happen.
      • unrefTimeout - [OPTIONAL] - If you have code that keeps the event loop running and want to stop the node process when that finishes regardless of the state of your cronjob, you can do so making use of this parameter. This is off by default and cron will run as if it needs to control the event loop. For more information take a look at timers#timers_timeout_unref from the NodeJS docs.
    • start - Runs your job.
    • stop - Stops your job.
    • setTime - Stops and changes the time for the CronJob. Param must be a CronTime.
    • lastDate - Tells you the last execution date.
    • nextDates - Provides an array of the next set of dates that will trigger an onTick.
    • fireOnTick - Allows you to override the onTick calling behavior. This matters so only do this if you have a really good reason to do so.
    • addCallback - Allows you to add onTick callbacks.
  • CronTime
    • constructor(time)
      • time - [REQUIRED] - The time to fire off your job. This can be in the form of cron syntax or a JS Date object.

Contributions

This is a community effort project. In the truest sense, this project started as an open source project from cron.js and grew into something else. Other people have contributed code, time, and oversight to the project. At this point there are too many to name here so I'll just say thanks.

Download Details:
 

Author: kelektiv
Download Link: Download The Source Code
Official Website: https://github.com/kelektiv/node-cron 
License: MIT license

#nodejs #javascript 

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Buddha Community

Node-Cron | A Simple Task Scheduler for Node.js

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

Hire Dedicated Node.js Developers - Hire Node.js Developers

If you look at the backend technology used by today’s most popular apps there is one thing you would find common among them and that is the use of NodeJS Framework. Yes, the NodeJS framework is that effective and successful.

If you wish to have a strong backend for efficient app performance then have NodeJS at the backend.

WebClues Infotech offers different levels of experienced and expert professionals for your app development needs. So hire a dedicated NodeJS developer from WebClues Infotech with your experience requirement and expertise.

So what are you waiting for? Get your app developed with strong performance parameters from WebClues Infotech

For inquiry click here: https://www.webcluesinfotech.com/hire-nodejs-developer/

Book Free Interview: https://bit.ly/3dDShFg

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Aria Barnes

Aria Barnes

1622719015

Why use Node.js for Web Development? Benefits and Examples of Apps

Front-end web development has been overwhelmed by JavaScript highlights for quite a long time. Google, Facebook, Wikipedia, and most of all online pages use JS for customer side activities. As of late, it additionally made a shift to cross-platform mobile development as a main technology in React Native, Nativescript, Apache Cordova, and other crossover devices. 

Throughout the most recent couple of years, Node.js moved to backend development as well. Designers need to utilize a similar tech stack for the whole web project without learning another language for server-side development. Node.js is a device that adjusts JS usefulness and syntax to the backend. 

What is Node.js? 

Node.js isn’t a language, or library, or system. It’s a runtime situation: commonly JavaScript needs a program to work, however Node.js makes appropriate settings for JS to run outside of the program. It’s based on a JavaScript V8 motor that can run in Chrome, different programs, or independently. 

The extent of V8 is to change JS program situated code into machine code — so JS turns into a broadly useful language and can be perceived by servers. This is one of the advantages of utilizing Node.js in web application development: it expands the usefulness of JavaScript, permitting designers to coordinate the language with APIs, different languages, and outside libraries.

What Are the Advantages of Node.js Web Application Development? 

Of late, organizations have been effectively changing from their backend tech stacks to Node.js. LinkedIn picked Node.js over Ruby on Rails since it took care of expanding responsibility better and decreased the quantity of servers by multiple times. PayPal and Netflix did something comparative, just they had a goal to change their design to microservices. We should investigate the motivations to pick Node.JS for web application development and when we are planning to hire node js developers. 

Amazing Tech Stack for Web Development 

The principal thing that makes Node.js a go-to environment for web development is its JavaScript legacy. It’s the most well known language right now with a great many free devices and a functioning local area. Node.js, because of its association with JS, immediately rose in ubiquity — presently it has in excess of 368 million downloads and a great many free tools in the bundle module. 

Alongside prevalence, Node.js additionally acquired the fundamental JS benefits: 

  • quick execution and information preparing; 
  • exceptionally reusable code; 
  • the code is not difficult to learn, compose, read, and keep up; 
  • tremendous asset library, a huge number of free aides, and a functioning local area. 

In addition, it’s a piece of a well known MEAN tech stack (the blend of MongoDB, Express.js, Angular, and Node.js — four tools that handle all vital parts of web application development). 

Designers Can Utilize JavaScript for the Whole Undertaking 

This is perhaps the most clear advantage of Node.js web application development. JavaScript is an unquestionable requirement for web development. Regardless of whether you construct a multi-page or single-page application, you need to know JS well. On the off chance that you are now OK with JavaScript, learning Node.js won’t be an issue. Grammar, fundamental usefulness, primary standards — every one of these things are comparable. 

In the event that you have JS designers in your group, it will be simpler for them to learn JS-based Node than a totally new dialect. What’s more, the front-end and back-end codebase will be basically the same, simple to peruse, and keep up — in light of the fact that they are both JS-based. 

A Quick Environment for Microservice Development 

There’s another motivation behind why Node.js got famous so rapidly. The environment suits well the idea of microservice development (spilling stone monument usefulness into handfuls or many more modest administrations). 

Microservices need to speak with one another rapidly — and Node.js is probably the quickest device in information handling. Among the fundamental Node.js benefits for programming development are its non-obstructing algorithms.

Node.js measures a few demands all at once without trusting that the first will be concluded. Many microservices can send messages to one another, and they will be gotten and addressed all the while. 

Versatile Web Application Development 

Node.js was worked in view of adaptability — its name really says it. The environment permits numerous hubs to run all the while and speak with one another. Here’s the reason Node.js adaptability is better than other web backend development arrangements. 

Node.js has a module that is liable for load adjusting for each running CPU center. This is one of numerous Node.js module benefits: you can run various hubs all at once, and the environment will naturally adjust the responsibility. 

Node.js permits even apportioning: you can part your application into various situations. You show various forms of the application to different clients, in light of their age, interests, area, language, and so on. This builds personalization and diminishes responsibility. Hub accomplishes this with kid measures — tasks that rapidly speak with one another and share a similar root. 

What’s more, Node’s non-hindering solicitation handling framework adds to fast, letting applications measure a great many solicitations. 

Control Stream Highlights

Numerous designers consider nonconcurrent to be one of the two impediments and benefits of Node.js web application development. In Node, at whatever point the capacity is executed, the code consequently sends a callback. As the quantity of capacities develops, so does the number of callbacks — and you end up in a circumstance known as the callback damnation. 

In any case, Node.js offers an exit plan. You can utilize systems that will plan capacities and sort through callbacks. Systems will associate comparable capacities consequently — so you can track down an essential component via search or in an envelope. At that point, there’s no compelling reason to look through callbacks.

 

Final Words

So, these are some of the top benefits of Nodejs in web application development. This is how Nodejs is contributing a lot to the field of web application development. 

I hope now you are totally aware of the whole process of how Nodejs is really important for your web project. If you are looking to hire a node js development company in India then I would suggest that you take a little consultancy too whenever you call. 

Good Luck!

Original Source

#node.js development company in india #node js development company #hire node js developers #hire node.js developers in india #node.js development services #node.js development

Node JS Development Company| Node JS Web Developers-SISGAIN

Top organizations and start-ups hire Node.js developers from SISGAIN for their strategic software development projects in Illinois, USA. On the off chance that you are searching for a first rate innovation to assemble a constant Node.js web application development or a module, Node.js applications are the most appropriate alternative to pick. As Leading Node.js development company, we leverage our profound information on its segments and convey solutions that bring noteworthy business results. For more information email us at hello@sisgain.com

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sophia tondon

sophia tondon

1625114985

Top 10 NodeJs app Development Companies- ValueCoders

Node.js is a prominent tech trend in the space of web and mobile application development. It has been proven very efficient and useful for a variety of application development. Thus, all business owners are eager to leverage this technology for creating their applications.

Are you striving to develop an application using Node.js? But can’t decide which company to hire for NodeJS app development? Well! Don’t stress over it, as the following list of NodeJS app development companies is going to help you find the best partner.

Let’s take a glance at top NodeJS application development companies to hire developers in 2021 for developing a mind-blowing application solution.

Before enlisting companies, I would like to say that every company has a foundation on which they thrive. Their end goals, qualities, and excellence define their competence. Thus, I prepared this list by considering a number of aspects. While making this list, I have considered the following aspects:

  • Review and rating
  • Enlisted by software peer & forums
  • Hourly price
  • Offered services
  • Year of experience (Average 8+ years)
  • Credibility & Excellence
  • Served clients and more

I believe this list will help you out in choosing the best NodeJS service provider company. So, now let’s explore the top NodeJS developer companies to choose from in 2021.

#1. JSGuru

JSGuru is a top-rated NodeJS app development company with an innovative team of dedicated NodeJS developers engaged in catering best-class UI/UX design, software products, and AWS professional services.

It is a team of one of the most talented developers to hire for all types of innovative solution development, including social media, dating, enterprise, and business-oriented solutions. The company has worked for years with a number of startups and launched a variety of products by collaborating with big-name corporations like T-systems.

If you want to hire NodeJS developers to secure an outstanding application, I would definitely suggest them. They serve in the area of eLearning, FinTech, eCommerce, Telecommunications, Mobile Device Management, and more.

  • Ratings: 4.9/5.0

  • Founded: 2006

  • Headquarters: Banja Luka, Bosnia, and Herzegovina

  • Price: Starting from $50/hour

Visit Website - https://www.valuecoders.com/blog/technology-and-apps/top-node-js-app-development-companies

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