1560824476
In this article, we’ll learn how to use most methods available in the nodeJS console class more effectively.
To demonstrate, I’ll use Chrome browser version 70.0.3538.77 and nodeJS version 8.11.** 3**.
Okay then. Let’s begin.
console.log(string, substitution)
While the famed console.log method really needs no introduction, you’ll be glad to know that the console.info and console.debug methods are identical to console.log in their operation.
You can use console.debug in the Firefox browser console by default but to use it in Chrome, you’ll have to set the log level to verbose like this.
The console.log method prints to standard out, whether this be the terminal or browser console. It outputs strings by default but can be used in conjuction with template strings to modify what it returns.
Here’s how it works:
The arguments in the template string are passed to util.format which then processes the arguments by replacing each substitution token with the respective converted value. The supported substitution tokens are:
const msg = `Using the console class`;
console.log('%s', msg); // Using the console class
console.log(msg); // Using the console class
%s is the default substitution pattern.
const circle = (radius = 1) => {
const profile = {};
const pi = 22/7;
profile.diameter = 2_pi_radius;
profile.circumference = pi_radius_2;
profile.area = pi_radius^2;
profile.volume = 4/3_pi_radius^3;
console.log('This circle has a radius of: %d cm', radius);
console.log('This circle has a circumference of: %f cm', profile.diameter);
console.log('This circle has an area of: %i cm^2', profile.area);
console.log('The profile of this cirlce is: %o', profile);
console.log('Diameter %d, Area: %f, Circumference %i', profile.diameter, profile.area, profile.circumference)
}
circle();
This is what happens:
%d will be substituted by a digit (integer or float). %f will be replaced by a float value. %i will be replaced by an integer. %o will be replaced by an Object.
%o is especially handy because we don’t have to use JSON.stringify to expand our object because it shows all the object’s properties by default.
Note that you can use as many token substitutions as you like. They’ll just be replaced the same order as the arguments you pass.
This substitution token applies css styles to the subsituted text.
console.log('LOG LEVEL: %c OK', 'color: green; font-weight: normal');
console.log('LOG LEVEL: %c PRIORITY', 'color: blue; font-weight: medium');
console.log('LOG LEVEL: %c WARN', 'color: red; font-weight: bold');
console.log('ERROR HERE');
Here it is in action.
Above, we note that the text we pass to console.log after the %c substitution token is affected by the styles, but the text before is left as is without styling.
The first argument passed to it is the data to be returned in the form of a table. The second is an array of selected columns to be displayed.
console.table(tabularData, [properties])
This method will print the input passed to it formatted as a table then log the input object after the table representation.
If an array is passed to it as data, each element in the array will be a row in the table.
const books = ['The Silmarillion', 'The Hobbit', 'Unfinished Tales'];
console.table(books);
With a simple array with a depth of 1, the first column in the table has the heading index. Under the index header in the first column are the array indexes and the items in the array are listed in the second column under the value header.
This is what happens for a nested array.
const authorsAndBooks = [['Tolkien', 'Lord of The Rings'],['Rutger', 'Utopia For Realists'], ['Sinek', 'Leaders Eat Last'], ['Eyal', 'Habit']];
console.table(authorsAndBooks);
For objects with a depth of 1, the object keys will be listed under the index header and the values in the object under the second column header.
const inventory = { apples: 200, mangoes: 50, avocados: 300, kiwis: 50 };
console.table(inventory);
For nested objects,
const forexConverter = { asia: { rupee: 1.39, renminbi: 14.59 , ringgit: 24.26 }, africa: { rand: 6.49, nakfa: 6.7 , kwanza:0.33 }, europe: { swissfranc: 101.60, gbp: 130, euro: 115.73 } };
console.table(forexConverter);
Some more nested objects,
const workoutLog = { Monday: { push: 'Incline Bench Press', pull: 'Deadlift'}, Wednesday: { push: 'Weighted Dips', pull: 'Barbell Rows'}};
console.table(workoutLog);
Here, we specify that we only want to see data under the column push.
console.table(workoutLog, 'push');
To sort the data under a column, just click the column header.
Pretty handy, eh?
Try passing console.table an object with some values as arrays!## console.dir
The first argument passed to this function is the object to be logged while the second is an object containing options that will define how the resulting output is fomatted or what properties in the object will be shown.
What’s returned is an object formatted by node’s util.inspect function.
Nested or child objects within the input object are expandable under disclosure triangles.
console.dir(object, options);
// where options = { showHidden: true ... }
Let’s see this in action.
const user = {
details: {
name: {
firstName: 'Immanuel',
lastName: 'Kant'
},
height: `1.83m"`,
weight: '90kg',
age: '80',
occupation: 'Philosopher',
nationality: 'German',
books: [
{
name: 'Critique of Pure Reason',
pub: '1781',
},
{
name: 'Critique of Judgement',
pub: '1790',
},
{
name: 'Critique of Practical Reason',
pub: '1788',
},
{
name: 'Perpetual Peace',
pub: '1795',
},
],
death: '1804'
}
}
console.dir(user);
Here it is in the Chrome console.
This function will render an interactive tree of the XML/HTML it is passed. It defaults to a Javascript object if it’s not possible to render the node tree.
console.dirxml(object|nodeList);
Much like console.*_dir, *_the rendered tree can be expanded through clicking disclosure triangles within which you can see child nodes.
It’s output is similar to that which we find under the Elements tab in the browser.
This is how it looks when we pass in some HTML from a Wikipedia page.
Let’s pass in some HTML from a page on this website.
This is how it looks when we pass in an object.
Try passing console.table an object with some values as arrays!## console.assert
The first argument passed to the function is a value to test as truthy. All other arguments passed are considered messages to be printed out if the value passed is not evaluated as truthy.
The Node REPL will throw an error halting execution of subsequent code.
console.assert(value, [...messages])
Here’s a basic example:
console.assert(false, 'Assertion failed'); // Assertion failed
Now, let’s have some fun. We’ll build a mini testing framework using console.assert
const sum = (a = 0, b = 0) => Number(a) + Number(b);
function test(functionName, actualFunctionResult, expected) {
const actual = actualFunctionResult;
const pass = actual === expected;
console.assert(pass, `Assertion failed for ${functionName}`);
return `Test passed ${actual} === ${expected}`;
}
console.log(test('sum', sum(1,1), 2)); // Test passed 2 === 2
console.log(test('sum', sum(), 0)); // Test passed 0 === 0
console.log(test('sum', sum, 2)); // Assertion failed for sum
console.log(test('sum', sum(3,3), 4)); // Assertion failed for sum
Run the above in your node REPL or browser console to see what happens.
These two are essentially identical. They will both print whatever string is passed to them.
However, console.warn prints out a triangle warn symbol before the message passed while console.error prints out a danger symbol before the message passed.
console.error(string, substitution);
console.warn(string, substitution);
Let’s note that string substitution can be applied in the same way as the console.log method.
Here’s a mini logging function using console.error.
const sum = (a = 0, b = 0) => Number(a) + Number(b);
function otherTest(actualFunctionResult, expected) {
if (actualFunctionResult !== expected) {
console.error(new Error(`Test failed ${actualFunctionResult} !== ${expected}`));
} else {
// pass
}
}
otherTest(sum(1,1), 3);
This console method will prints the string Trace: followed by the label passed to the function then the stack trace to the current position of the function.
function getCapital(country) {
const capitalMap = {
belarus: 'minsk', australia: 'canberra', egypt: 'cairo', georgia: 'tblisi', latvia: 'riga', samoa: 'apia'
};
console.trace('Start trace here');
return Object.keys(capitalMap).find(item => item === country) ? capitalMap[country] : undefined;
}
console.log(getCapital('belarus'));
console.log(getCapital('accra'));
Count will begin and increment a counter of name label** .**
Let’s build a word counter to see how it works.
const getOccurences = (word = 'foolish') => {
const phrase = `Oh me! Oh life! of the questions of these recurring, Of the endless trains of the faithless, of cities fill’d with the foolish, Of myself forever reproaching myself, for who more foolish than I, and who more faithless?`;
let count = 0;
const wordsFromPhraseArray = phrase.replace(/[,.!?]/igm, '').split(' ');
wordsFromPhraseArray.forEach((element, idx) => {
if (element === word) {
count ++;
console.count(word);
}
});
return count;
}
getOccurences();
Here, we see that the word foolish was logged twice. Once for each appearance of the word in the phrase.
We could use this as a handy method to see how many times a function was called or how many times a line in our code executed.
As the name suggests, this resets a counter having a label set by the console.count method.
const getOccurences = (word = 'foolish') => {
const phrase = `Oh me! Oh life! of the questions of these recurring, Of the endless trains of the faithless, of cities fill’d with the foolish, Of myself forever reproaching myself, for who more foolish than I, and who more faithless?`;
let count = 0;
const wordsFromPhraseArray = phrase.replace(/[,.!?]/igm, '').split(' ');
wordsFromPhraseArray.forEach((element, idx) => {
if (element === word) {
count ++;
console.count(word);
console.countReset(word);
}
});
return count;
}
getOccurences();
We can see that our getOccurences function returns 2 because there are indeed two occurences of the word foolish in the phrase but since our counter is reset at every match, it logs foolish: 1twice.
The console.time function starts a timer with the label supplied as an argument to the function, while the console.*_timeEnd *_function stops a timer with the **label supplied as an argument to the function.
console.time('<timer-label>');
console.timeEnd('<timer-label'>);
We can use it to figure out how much time it took to run an operation by passing in the same label name to both functions.
const users = ['Vivaldi', 'Beethoven', 'Ludovico'];
const loop = (array) => {
array.forEach((element, idx) => {
console.log(element);
})
}
const timer = () => {
console.time('timerLabel');
loop(users);
console.timeEnd('timerLabel');
}
timer();
We can see the timer label displayed against time value after the timer is stopped.
It took the loop function 0.6909ms to finish looping through the array.
At last, we’ve come to the end of this tutorial. I hope you’ve enjoyed it.
I’ve left out the non standard uses of the console class like console.profile, console.profileEnd and console.timeLog , but feel free to experiment with them and let me know how it goes.
☞ The Complete Node.js Developer Course (2nd Edition)
☞ GraphQL: Learning GraphQL with Node.Js
☞ Angular (Angular 2+) & NodeJS - The MEAN Stack Guide
☞ Beginner Full Stack Web Development: HTML, CSS, React & Node
☞ Node with React: Fullstack Web Development
☞ MERN Stack Front To Back: Full Stack React, Redux & Node.js
#node-js
1632537859
Not babashka. Node.js babashka!?
Ad-hoc CLJS scripting on Node.js.
Experimental. Please report issues here.
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:
Nbb requires Node.js v12 or newer.
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)'
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
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
.
$ 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
.
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 [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.
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
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]))
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.
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:
:syms
.-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.
See this gist on how to convert an nbb script or project to shadow-cljs.
Prequisites:
To build:
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
1622719015
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.
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.
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.
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:
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).
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.
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.
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.
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.
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!
#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
1616671994
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
#hire dedicated node.js developers #hire node.js developers #hire top dedicated node.js developers #hire node.js developers in usa & india #hire node js development company #hire the best node.js developers & programmers
1616839211
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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1625114985
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:
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
#node js developer #hire node js developer #hiring node js developers #node js development company #node.js development company #node js development services