1559198041
JavaScript Web Workers: A Beginner’s Guide
Learn how web workers help with web app performance, and get started by building a basic JavaScript web worker.
In 2019, the web ecosystem has evolved to the point where the browser is an execution environment for applications built on JavaScript. This is reflected in the speed with which the industry comes up with new frameworks, paradigms, module loaders and bundlers, dependency managers, build tools, and package managers year after year.
When JavaScript was conceived in the early days of the internet, the direction of internet development was not clear. Due to the constant, rapid change in the industry and ecosystem, the need for the backward-compatibility of browsers and web standards, the evolution of JavaScript became a constant stream of patches, hacks and afterthoughts.
Today’s mobile devices normally come with 8+ CPU cores, or 12+ GPU cores. Desktop and server CPUs have up to 16 cores, 32 threads, or more.
In this environment, having a dominant programming or scripting environment that is single-threaded is a bottleneck.
JavaScript Is Single-threaded
This means that by design, JavaScript engines — originally browsers — have one main thread of execution, and, to put it simply, process or function B cannot be executed until process or function A is finished. A web page’s UI is unresponsive to any other JavaScript processing while it is occupied with executing something — this is known as DOM blocking.
This is terribly inefficient, especially compared to other languages.
If we go to JS Bin and run this code in the browser’s JavaScript console:
//noprotect
i = 0;
while (i < 60000) {
console.log("The number is " + i);
i++;
}
… the whole jsbin.com website will become unresponsive until the browser counts — and logs — to 60,000.
We won’t be able to interact with anything on the page, because the browser is busy.
Now, this is a relatively undemanding computing process, and today’s web apps often involve much more demanding tasks.
We need to be able to compute things in the background while the user seamlessly interacts with the page.
Web Workers
The W3C published a first draft of the web workers standard in 2009. The full specification can be found on the Web Hypertext Application Technology Working Group website — or WHATWG — a web standards body alternative to W3C.
Web workers is an asynchronous system, or protocol, for web pages to execute tasks in the background, independently from the main thread and website UI. It is an isolated environment that is insulated from the window object, the document object, direct internet access and is best suited for long-running or demanding computational tasks.
Apart from web workers — a system dedicated to multithreading — there are other ways to achieve asnychronous processing in JavaScript, such as asynchronous Ajax calls, and event loop.
To demonstrate this, we will go back to JS Bin and try this snippet:
console.log("A");
setTimeout(function(){console.log("B");},2000);
console.log("C");
setTimeout(function(){console.log("D");},0);
console.log("E");
setTimeout(function(){console.log("F");},1000);
When we run this, our log sequence is A, C, E, D, F, B. The browser first schedules operations without the timeout, as they come, and then it executes the setTimeout() functions in the order of their respective specified delays. However, this asynchronicity should not be automatically conflated with multithreading. Depending on the host machine, this can often be just a single-thread stack of the calls in the order we explained.
Web Workers & Multithreading
As Mozilla’s JavaScript reference website explains, web workers are a “means for web content to run scripts in background threads.”
We use them in the following way: we check for the availability of the Worker() constructor in the browser, and if it is available, we instantiate a worker object, with the script URL as the argument. This script will be executed on a separate thread.
The script must be served from the same host or domain for security reasons, and that is also the reason that web workers won’t work if we open the file locally with a file:// scheme.
if (typeof(Worker) !== "undefined") {
worker = new Worker("worker.js");
}
Now we define this code in the worker.js file:
i = 0;
while (i < 200000) {
postMessage("Web Worker Counter: " + i);
i++;
}
The Separation of Threads
An important thing to note here is the separation of the window and document scope of execution in the main browser window thread, and the worker scope.
In order to make use of the worker thread, these two scopes need to be able to communicate. To achieve this, we use the postMessage() function within the worker.js file — to send messages to the main browser thread — and the worker.onmessage listener in the main thread to listen to worker messages.
We can also send messages from the main browser thread to the worker thread or function. The only difference is that we reverse things, and call worker.postMessage() on the main thread, and onmessage on the worker thread. To quote Mozilla’s developer reference:
Notice that
onmessageandpostMessage()need to be hung off theWorkerobject when used in the main script thread, but not when used in the worker. This is because, inside the worker, the worker is effectively the global scope.
We can use theterminate()method in the same way, to end our worker’s execution.
With all this in mind, we come to this example:
index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>Web Workers Example</title>
<style type="text/css">
body {padding-top:28px;}
.output-cont {margin-left:12%; margin-top:28px;}
.output-cont h3 {width:200px; height:100%;}
.output-cont button {padding:4px 8px; font-size:1.1rem; font-family:sans-serif; }
</style>
</head>
<body>
<div class="output-cont"><button onclick="testWorker()">start worker</button><h3 id="workerOutput"></h3><button onclick="terminateWorker()">terminate worker</button></div>
<br/>
<div class="output-cont"><button onclick="testMainThread()">start blocking thread</button><h3 id="mainThreadOutput"></h3></div>
<br/>
<div class="output-cont"><button onclick="alert('browser responsive!')">test browser responsiveness</button></div>
<script>
var worker;
function testWorker() {
if (typeof(Worker) !== "undefined") {
if (typeof(worker) == "undefined") {
worker = new Worker("worker.js");
}
worker.onmessage = function(event) {
document.getElementById("workerOutput").innerHTML = event.data;
};
} else {
document.getElementById("workerOutput").innerHTML = "Web Workers are not supported in your browser";
}
}
function terminateWorker() {
worker.terminate();
worker = undefined;
}
function testMainThread() {
for (var i = 0; i < 200000; i++) {
document.getElementById("mainThreadOutput").innerHTML = "Main Thread Counter: " + i;
}
}
</script>
</body>
</html>
and worker.js:
i = 0;
while (i < 200000) {
postMessage("Web Worker Counter: " + i);
i++;
}
This gives us the opportunity to test out the effects of main-thread execution on page behavior and performance versus the web worker’s effects.
In this tutorial, we used http-server to serve the files locally.
Now we can see that the worker thread does not block the interactivity of the main browser process, and looping through 200,000 numbers does not affect the main thread. The numbers in the #workerOutput element are updated on every iteration.
The blocking thread, or main thread, when engaged in a loop, blocks all interactivity (we have set the number of iterations to 200,000 here, but it will be even more obvious if we increase it to 2,000,000).
One more thing that points us to a blocked main thread is that the worker process updates the page on every iteration, and the loop in the main thread (the one defined in index.html) only updates the #mainThreadOutput element on the last iteration.
This is because the browser is too consumed with counting (for loop) to be able to redraw the DOM, so it does it only once its business with the for loop is fully done (at the end of the loop).
Conclusion
In this article, we introduced web workers, a technology that helps the web industry keep up with more and more demanding web apps. This is done by providing a way for web apps to leverage multi-processor and multi-threaded devices by bestowing some multi-threaded superpowers to JavaScript.
Web workers turn the mobile and desktop browser environments into application platforms, providing them with a strict execution environment. This strictness may force us to provide for the copying of objects between multiple threads, and to plan our applications with these constraints in mind.
Do you have any tips regarding web workers, and the web as a programming platform? Let us know in the comments!
#javascript #web-development
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1656151740
Test_cov_console: Flutter Console Coverage Test
Flutter Console Coverage Test
This small dart tools is used to generate Flutter Coverage Test report to console
How to install
Add a line like this to your package's pubspec.yaml (and run an implicit flutter pub get):
dev_dependencies:
test_cov_console: ^0.2.2
How to run
run the following command to make sure all flutter library is up-to-date
flutter pub get
Running "flutter pub get" in coverage... 0.5s
run the following command to generate lcov.info on coverage directory
flutter test --coverage
00:02 +1: All tests passed!
run the tool to generate report from lcov.info
flutter pub run test_cov_console
---------------------------------------------|---------|---------|---------|-------------------|
File |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/ | | | | |
print_cov.dart | 100.00 | 100.00 | 88.37 |...,149,205,206,207|
print_cov_constants.dart | 0.00 | 0.00 | 0.00 | no unit testing|
lib/ | | | | |
test_cov_console.dart | 0.00 | 0.00 | 0.00 | no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
All files with unit testing | 100.00 | 100.00 | 88.37 | |
---------------------------------------------|---------|---------|---------|-------------------|
Optional parameter
If not given a FILE, "coverage/lcov.info" will be used.
-f, --file=<FILE> The target lcov.info file to be reported
-e, --exclude=<STRING1,STRING2,...> A list of contains string for files without unit testing
to be excluded from report
-l, --line It will print Lines & Uncovered Lines only
Branch & Functions coverage percentage will not be printed
-i, --ignore It will not print any file without unit testing
-m, --multi Report from multiple lcov.info files
-c, --csv Output to CSV file
-o, --output=<CSV-FILE> Full path of output CSV file
If not given, "coverage/test_cov_console.csv" will be used
-t, --total Print only the total coverage
Note: it will ignore all other option (if any), except -m
-p, --pass=<MINIMUM> Print only the whether total coverage is passed MINIMUM value or not
If the value >= MINIMUM, it will print PASSED, otherwise FAILED
Note: it will ignore all other option (if any), except -m
-h, --help Show this help
example run the tool with parameters
flutter pub run test_cov_console --file=coverage/lcov.info --exclude=_constants,_mock
---------------------------------------------|---------|---------|---------|-------------------|
File |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/ | | | | |
print_cov.dart | 100.00 | 100.00 | 88.37 |...,149,205,206,207|
lib/ | | | | |
test_cov_console.dart | 0.00 | 0.00 | 0.00 | no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
All files with unit testing | 100.00 | 100.00 | 88.37 | |
---------------------------------------------|---------|---------|---------|-------------------|
report for multiple lcov.info files (-m, --multi)
It support to run for multiple lcov.info files with the followings directory structures:
1. No root module
<root>/<module_a>
<root>/<module_a>/coverage/lcov.info
<root>/<module_a>/lib/src
<root>/<module_b>
<root>/<module_b>/coverage/lcov.info
<root>/<module_b>/lib/src
...
2. With root module
<root>/coverage/lcov.info
<root>/lib/src
<root>/<module_a>
<root>/<module_a>/coverage/lcov.info
<root>/<module_a>/lib/src
<root>/<module_b>
<root>/<module_b>/coverage/lcov.info
<root>/<module_b>/lib/src
...
You must run test_cov_console on <root> dir, and the report would be grouped by module, here is
the sample output for directory structure 'with root module':
flutter pub run test_cov_console --file=coverage/lcov.info --exclude=_constants,_mock --multi
---------------------------------------------|---------|---------|---------|-------------------|
File |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/ | | | | |
print_cov.dart | 100.00 | 100.00 | 88.37 |...,149,205,206,207|
lib/ | | | | |
test_cov_console.dart | 0.00 | 0.00 | 0.00 | no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
All files with unit testing | 100.00 | 100.00 | 88.37 | |
---------------------------------------------|---------|---------|---------|-------------------|
---------------------------------------------|---------|---------|---------|-------------------|
File - module_a - |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/ | | | | |
print_cov.dart | 100.00 | 100.00 | 88.37 |...,149,205,206,207|
lib/ | | | | |
test_cov_console.dart | 0.00 | 0.00 | 0.00 | no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
All files with unit testing | 100.00 | 100.00 | 88.37 | |
---------------------------------------------|---------|---------|---------|-------------------|
---------------------------------------------|---------|---------|---------|-------------------|
File - module_b - |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/ | | | | |
print_cov.dart | 100.00 | 100.00 | 88.37 |...,149,205,206,207|
lib/ | | | | |
test_cov_console.dart | 0.00 | 0.00 | 0.00 | no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
All files with unit testing | 100.00 | 100.00 | 88.37 | |
---------------------------------------------|---------|---------|---------|-------------------|
Output to CSV file (-c, --csv, -o, --output)
flutter pub run test_cov_console -c --output=coverage/test_coverage.csv
#### sample CSV output file:
File,% Branch,% Funcs,% Lines,Uncovered Line #s
lib/,,,,
test_cov_console.dart,0.00,0.00,0.00,no unit testing
lib/src/,,,,
parser.dart,100.00,100.00,97.22,"97"
parser_constants.dart,100.00,100.00,100.00,""
print_cov.dart,100.00,100.00,82.91,"29,49,51,52,171,174,177,180,183,184,185,186,187,188,279,324,325,387,388,389,390,391,392,393,394,395,398"
print_cov_constants.dart,0.00,0.00,0.00,no unit testing
All files with unit testing,100.00,100.00,86.07,""Installing
Use this package as an executable
Install it
You can install the package from the command line:
dart pub global activate test_cov_consoleUse it
The package has the following executables:
$ test_cov_console
Use this package as a library
Depend on it
Run this command:
With Dart:
$ dart pub add test_cov_consoleWith Flutter:
$ flutter pub add test_cov_consoleThis will add a line like this to your package's pubspec.yaml (and run an implicit dart pub get):
dependencies:
test_cov_console: ^0.2.2Alternatively, your editor might support dart pub get or flutter pub get. Check the docs for your editor to learn more.
Import it
Now in your Dart code, you can use:
import 'package:test_cov_console/test_cov_console.dart';example/lib/main.dart
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.blue,
// This makes the visual density adapt to the platform that you run
// the app on. For desktop platforms, the controls will be smaller and
// closer together (more dense) than on mobile platforms.
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key? key, required this.title}) : super(key: key);
// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.
// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}
@override
Widget build(BuildContext context) {
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Invoke "debug painting" (press "p" in the console, choose the
// "Toggle Debug Paint" action from the Flutter Inspector in Android
// Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
// to see the wireframe for each widget.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}Author: DigitalKatalis
Source Code: https://github.com/DigitalKatalis/test_cov_console
License: BSD-3-Clause license
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1624298400
Learn JavaScript - Full Course for Beginners. DO NOT MISS!!!
This complete 134-part JavaScript tutorial for beginners will teach you everything you need to know to get started with the JavaScript programming language.
⭐️Course Contents⭐️
0:00:00 Introduction
0:01:24 Running JavaScript
0:04:23 Comment Your Code
0:05:56 Declare Variables
0:06:15 Storing Values with the Assignment Operator
0:11:31 Initializing Variables with the Assignment Operator
0:11:58 Uninitialized Variables
0:12:40 Case Sensitivity in Variables
0:14:05 Add Two Numbers
0:14:34 Subtract One Number from Another
0:14:52 Multiply Two Numbers
0:15:12 Dividing Numbers
0:15:30 Increment
0:15:58 Decrement
0:16:22 Decimal Numbers
0:16:48 Multiply Two Decimals
0:17:18 Divide Decimals
0:17:33 Finding a Remainder
0:18:22 Augmented Addition
0:19:22 Augmented Subtraction
0:20:18 Augmented Multiplication
0:20:51 Augmented Division
0:21:19 Declare String Variables
0:22:01 Escaping Literal Quotes
0:23:44 Quoting Strings with Single Quotes
0:25:18 Escape Sequences
0:26:46 Plus Operator
0:27:49 Plus Equals Operator
0:29:01 Constructing Strings with Variables
0:30:14 Appending Variables to Strings
0:31:11 Length of a String
0:32:01 Bracket Notation
0:33:27 Understand String Immutability
0:34:23 Find the Nth Character
0:34:51 Find the Last Character
0:35:48 Find the Nth-to-Last Character
0:36:28 Word Blanks
0:40:44 Arrays
0:41:43 Nest Arrays
0:42:33 Access Array Data
0:43:34 Modify Array Data
0:44:48 Access Multi-Dimensional Arrays
0:46:30 push()
0:47:29 pop()
0:48:33 shift()
0:49:23 unshift()
0:50:36 Shopping List
0:51:41 Write Reusable with Functions
0:53:41 Arguments
0:55:43 Global Scope
0:59:31 Local Scope
1:00:46 Global vs Local Scope in Functions
1:02:40 Return a Value from a Function
1:03:55 Undefined Value returned
1:04:52 Assignment with a Returned Value
1:05:52 Stand in Line
1:08:41 Boolean Values
1:09:24 If Statements
1:11:51 Equality Operator
1:13:18 Strict Equality Operator
1:14:43 Comparing different values
1:15:38 Inequality Operator
1:16:20 Strict Inequality Operator
1:17:05 Greater Than Operator
1:17:39 Greater Than Or Equal To Operator
1:18:09 Less Than Operator
1:18:44 Less Than Or Equal To Operator
1:19:17 And Operator
1:20:41 Or Operator
1:21:37 Else Statements
1:22:27 Else If Statements
1:23:30 Logical Order in If Else Statements
1:24:45 Chaining If Else Statements
1:27:45 Golf Code
1:32:15 Switch Statements
1:35:46 Default Option in Switch Statements
1:37:23 Identical Options in Switch Statements
1:39:20 Replacing If Else Chains with Switch
1:41:11 Returning Boolean Values from Functions
1:42:20 Return Early Pattern for Functions
1:43:38 Counting Cards
1:49:11 Build Objects
1:50:46 Dot Notation
1:51:33 Bracket Notation
1:52:47 Variables
1:53:34 Updating Object Properties
1:54:30 Add New Properties to Object
1:55:19 Delete Properties from Object
1:55:54 Objects for Lookups
1:57:43 Testing Objects for Properties
1:59:15 Manipulating Complex Objects
2:01:00 Nested Objects
2:01:53 Nested Arrays
2:03:06 Record Collection
2:10:15 While Loops
2:11:35 For Loops
2:13:56 Odd Numbers With a For Loop
2:15:28 Count Backwards With a For Loop
2:17:08 Iterate Through an Array with a For Loop
2:19:43 Nesting For Loops
2:22:45 Do…While Loops
2:24:12 Profile Lookup
2:28:18 Random Fractions
2:28:54 Random Whole Numbers
2:30:21 Random Whole Numbers within a Range
2:31:46 parseInt Function
2:32:36 parseInt Function with a Radix
2:33:29 Ternary Operator
2:34:57 Multiple Ternary Operators
2:36:57 var vs let
2:39:02 var vs let scopes
2:41:32 const Keyword
2:43:40 Mutate an Array Declared with const
2:44:52 Prevent Object Mutation
2:47:17 Arrow Functions
2:28:24 Arrow Functions with Parameters
2:49:27 Higher Order Arrow Functions
2:53:04 Default Parameters
2:54:00 Rest Operator
2:55:31 Spread Operator
2:57:18 Destructuring Assignment: Objects
3:00:18 Destructuring Assignment: Nested Objects
3:01:55 Destructuring Assignment: Arrays
3:03:40 Destructuring Assignment with Rest Operator to Reassign Array
3:05:05 Destructuring Assignment to Pass an Object
3:06:39 Template Literals
3:10:43 Simple Fields
3:12:24 Declarative Functions
3:12:56 class Syntax
3:15:11 getters and setters
3:20:25 import vs require
3:22:33 export
3:23:40 * to Import
3:24:50 export default
3:25:26 Import a Default Export
📺 The video in this post was made by freeCodeCamp.org
The origin of the article: https://www.youtube.com/watch?v=PkZNo7MFNFg&list=PLWKjhJtqVAblfum5WiQblKPwIbqYXkDoC&index=4
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Thanks for visiting and watching! Please don’t forget to leave a like, comment and share!
#javascript #learn javascript #learn javascript for beginners #learn javascript - full course for beginners #javascript programming language
1594720956
A Beginner’s Guide to … in JavaScript
What is … ?
The ‘…’ or spread operator is a useful tool for syntax in JavaScript. It can be used in:
- Function calls
- Arrays/Strings
- Rest Parameters
Let’s go through how to use it in each of the mentioned uses.
Function Calls
1. ‘new’ object using array
Traditionally, you cannot use the ‘new’ keyword to create an object using an array directly. I’m talking about something like a new Date(array) (a new Date Object). Using an array in the constructor is not valid but with ‘…’ , it becomes possible:
const date = [2020, 0, 1]; // 1 Jan 2020
const dateObj = new Date(...date);
console.log(dateObj);
// VM60:1 Wed Jan 01 2020 00:00:00 GMT-0500 (Eastern Standard Time)
2. ‘apply()’ method
The ‘…’ can be used just like the apply() method in JavaScript.
For example, instead of using apply():
const array = ['a', 'b'];
const elements = [0, 1, 2];
array.push.apply(array, elements);
console.info(array); // ["a", "b", 0, 1, 2]
You can use ‘…’ for a more concise syntax like so:
const array = ['a', 'b'];
const elements = [0, 1, 2];
array.push(...elements);
console.info(array); // ["a", "b", 0, 1, 2]
For more details on how
_apply()_works, you can read up at w3schools.com/js/js_function_apply.asp.
#beginners-guide #javascript #web-development #programming
1624379820
JavaScript Tutorial for Beginners: Learn JavaScript in 1 Hour
Watch this JavaScript tutorial for beginners to learn JavaScript basics in one hour.
avaScript is one of the most popular programming languages in 2019. A lot of people are learning JavaScript to become front-end and/or back-end developers.
I’ve designed this JavaScript tutorial for beginners to learn JavaScript from scratch. We’ll start off by answering the frequently asked questions by beginners about JavaScript and shortly after we’ll set up our development environment and start coding.
Whether you’re a beginner and want to learn to code, or you know any programming language and just want to learn JavaScript for web development, this tutorial helps you learn JavaScript fast.
You don’t need any prior experience with JavaScript or any other programming languages. Just watch this JavaScript tutorial to the end and you’ll be writing JavaScript code in no time.
If you want to become a front-end developer, you have to learn JavaScript. It is the programming language that every front-end developer must know.
You can also use JavaScript on the back-end using Node. Node is a run-time environment for executing JavaScript code outside of a browser. With Node and Express (a popular JavaScript framework), you can build back-end of web and mobile applications.
If you’re looking for a crash course that helps you get started with JavaScript quickly, this course is for you.
⭐️TABLE OF CONTENT ⭐️
00:00 What is JavaScript
04:41 Setting Up the Development Environment
07:52 JavaScript in Browsers
11:41 Separation of Concerns
13:47 JavaScript in Node
16:11 Variables
21:49 Constants
23:35 Primitive Types
26:47 Dynamic Typing
30:06 Objects
35:22 Arrays
39:41 Functions
44:22 Types of Functions
📺 The video in this post was made by Programming with Mosh
The origin of the article: https://www.youtube.com/watch?v=W6NZfCO5SIk&list=PLTjRvDozrdlxEIuOBZkMAK5uiqp8rHUax&index=2
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