Joel Kelly

Joel Kelly

1565062140

An Overview of ES6 Classes

JavaScript introduced the class keyword in 2015 with the release of ES6. React made classes an indispensable language feature when they introduced support for using extends React.Component instead of React.createClass() in 2015, and removed support for React.createClass() entirely in 2017 in favor of classes. Today, classes are a fundamental part of JavaScript, and many new JavaScript devs don’t remember a time before classes. In this article, I’ll provide an overview of how classes work in JavaScript: how to declare classes, what features JavaScript provides with classes, and how inheritance works.

Working With Classes

Here’s how you define a basic class MyClass, and create an instance of MyClass.

class MyClass {
  constructor() {
    this.answer = 42;
  }
}

const obj = new MyClass();
obj.answer; // 42

You must instantiate a class with new. Calling MyClass() without new throws an error:

// TypeError: Class constructor MyClass cannot be invoked without 'new'
MyClass();

A class is technically a function, although the ECMAScript spec explicitly disallows calling a class without new. In fact, the typeof operator identifies MyClass as a function.

typeof MyClass; // 'function'
MyClass instanceof Function; //  true

To check whether an object is an instance of a class, you should use the instanceof operator. You can also check whether the constructor property is equal to MyClass.

obj instanceof MyClass; // true
// Works, but `instanceof` is better...
obj.constructor === MyClass;

// Because `instanceof` is immune to overwriting the `constructor` property
const obj = {};
obj.constructor = MyClass;
obj instanceof MyClass; // false
obj.constructor === MyClass; // true

Like functions, classes in JavaScript are variables like any other. You can assign a class to a variable, overwrite that class, and pass a class as a parameter to a function. Like functions, you can also declare classes with or without explicit names.

let Foo = class {
  constructor() {
    this.answer = 42;
  }
}

Foo = class {
  constructor() {
    this.answer = 43;
  }
}

console.log(Foo); // '[Function: Foo]'
console.log(new Foo()); // 'Foo { answer: 43 }'

Unlike functions, classes are never hoisted. In the below example the function Foo() prints successfully, because JavaScript looks ahead and ‘hoists’ Foo() to the top of the function. But trying to print the class Bar throws a reference error, because JavaScript does not hoist class definitions.

#es6 #javascript #web-development #programming #developer

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Buddha Community

An Overview of ES6 Classes
Lawrence  Lesch

Lawrence Lesch

1662107520

Superdom: Better and Simpler ES6 DOM Manipulation

Superdom

You have dom. It has all the DOM virtually within it. Use that power:

// Fetch all the page links
let links = dom.a.href;

// Links open in a new tab
dom.a.target = '_blank';

Only for modern browsers

Getting started

Simply use the CDN via unpkg.com:

<script src="https://unpkg.com/superdom@1"></script>

Or use npm or bower:

npm|bower install superdom --save

Select

It always returns an array with the matched elements. Get all the elements that match the selector:

// Simple element selector into an array
let allLinks = dom.a;

// Loop straight on the selection
dom.a.forEach(link => { ... });

// Combined selector
let importantLinks = dom['a.important'];

There are also some predetermined elements, such as id, class and attr:

// Select HTML Elements by id:
let main = dom.id.main;

// by class:
let buttons = dom.class.button;

// or by attribute:
let targeted = dom.attr.target;
let targeted = dom.attr['target="_blank"'];

Generate

Use it as a function or a tagged template literal to generate DOM fragments:

// Not a typo; tagged template literals
let link = dom`<a href="https://google.com/">Google</a>`;

// It is the same as
let link = dom('<a href="https://google.com/">Google</a>');

Delete elements

Delete a piece of the DOM

// Delete all of the elements with the class .google
delete dom.class.google;   // Is this an ad-block rule?

Attributes

You can easily manipulate attributes right from the dom node. There are some aliases that share the syntax of the attributes such as html and text (aliases for innerHTML and textContent). There are others that travel through the dom such as parent (alias for parentNode) and children. Finally, class behaves differently as explained below.

Get attributes

The fetching will always return an array with the element for each of the matched nodes (or undefined if not there):

// Retrieve all the urls from the page
let urls = dom.a.href;     // #attr-list
  // ['https://google.com', 'https://facebook.com/', ...]

// Get an array of the h2 contents (alias of innerHTML)
let h2s = dom.h2.html;     // #attr-alias
  // ['Level 2 header', 'Another level 2 header', ...]

// Get whether any of the attributes has the value "_blank"
let hasBlank = dom.class.cta.target._blank;    // #attr-value
  // true/false

You also use these:

  • html (alias of innerHTML): retrieve a list of the htmls
  • text (alias of textContent): retrieve a list of the htmls
  • parent (alias of parentNode): travel up one level
  • children: travel down one level

Set attributes

// Set target="_blank" to all links
dom.a.target = '_blank';     // #attr-set
dom.class.tableofcontents.html = `
  <ul class="tableofcontents">
    ${dom.h2.map(h2 => `
      <li>
        <a href="#${h2.id}">
          ${h2.innerHTML}
        </a>
      </li>
    `).join('')}
  </ul>
`;

Remove an attribute

To delete an attribute use the delete keyword:

// Remove all urls from the page
delete dom.a.href;

// Remove all ids
delete dom.a.id;

Classes

It provides an easy way to manipulate the classes.

Get classes

To retrieve whether a particular class is present or not:

// Get an array with true/false for a single class
let isTest = dom.a.class.test;     // #class-one

For a general method to retrieve all classes you can do:

// Get a list of the classes of each matched element
let arrays = dom.a.class;     // #class-arrays
  // [['important'], ['button', 'cta'], ...]

// If you want a plain list with all of the classes:
let flatten = dom.a.class._flat;     // #class-flat
  // ['important', 'button', 'cta', ...]

// And if you just want an string with space-separated classes:
let text = dom.a.class._text;     // #class-text
  // 'important button cta ...'

Add a class

// Add the class 'test' (different ways)
dom.a.class.test = true;    // #class-make-true
dom.a.class = 'test';       // #class-push

Remove a class

// Remove the class 'test'
dom.a.class.test = false;    // #class-make-false

Manipulate

Did we say it returns a simple array?

dom.a.forEach(link => link.innerHTML = 'I am a link');

But what an interesting array it is; indeed we are also proxy'ing it so you can manipulate its sub-elements straight from the selector:

// Replace all of the link's html with 'I am a link'
dom.a.html = 'I am a link';

Of course we might want to manipulate them dynamically depending on the current value. Just pass it a function:

// Append ' ^_^' to all of the links in the page
dom.a.html = html => html + ' ^_^';

// Same as this:
dom.a.forEach(link => link.innerHTML = link.innerHTML + ' ^_^');

Note: this won't work dom.a.html += ' ^_^'; for more than 1 match (for reasons)

Or get into genetics to manipulate the attributes:

dom.a.attr.target = '_blank';

// Only to external sites:
let isOwnPage = el => /^https?\:\/\/mypage\.com/.test(el.getAttribute('href'));
dom.a.attr.target = (prev, i, element) => isOwnPage(element) ? '' : '_blank';

Events

You can also handle and trigger events:

// Handle click events for all <a>
dom.a.on.click = e => ...;

// Trigger click event for all <a>
dom.a.trigger.click;

Testing

We are using Jest as a Grunt task for testing. Install Jest and run in the terminal:

grunt watch

Download Details:

Author: franciscop
Source Code: https://github.com/franciscop/superdom 
License: MIT license

#javascript #es6 #dom 

Yashi Tyagi

1617449307

CA Classes - Best CA Classes Online

Chartered Accountancy course requires mental focus & discipline, coaching for CA Foundation, CA Inter and CA Finals are omnipresent, and some of the best faculty’s classes have moved online, in this blog, we are going to give the best way to find online videos lectures, various online websites provide the CA lectures, Smartnstudy one of the best site to CA preparation, here all faculty’s video lecture available.

check here : ca classes

#ca classes online #ca classes in delhi #ca classes app #ca pendrive classes #ca google drive classes #best ca classes online

Duy  Tien

Duy Tien

1626358620

Sử dụng Class trong ES6 #8

Sử dụng Class trong ES6

#class #es6

Joseph  Murray

Joseph Murray

1624048020

How to Find All the Classes of a Package in Java

In this article let’s take a look at how to find all classes of a package in Java

To find all classes of a package in Java we can use the ClassHunter of Burningwave Core library. So we start by adding the following dependency to our pom.xml:

XML

1

<dependency>2
    <groupId>org.burningwave</groupId>3
    <artifactId>core</artifactId>4
    <version>8.4.0</version>5
</dependency>

The next steps are the following:

  • retrieving the ClassHunter through the ComponentContainer
  • defining a regular expression that we must pass to the **ClassCriteria **object that will be injected into the **SearchConfig **object
  • calling the **loadInCache **method that loads in the cache all loadable classes of the indicated paths, then applies the criteria filter and then returns the **SearchResult **object which contains the classes that match the criteria

#java #classes #class #packages #package #how to find all the classes of a package in java

Joel Kelly

Joel Kelly

1565062140

An Overview of ES6 Classes

JavaScript introduced the class keyword in 2015 with the release of ES6. React made classes an indispensable language feature when they introduced support for using extends React.Component instead of React.createClass() in 2015, and removed support for React.createClass() entirely in 2017 in favor of classes. Today, classes are a fundamental part of JavaScript, and many new JavaScript devs don’t remember a time before classes. In this article, I’ll provide an overview of how classes work in JavaScript: how to declare classes, what features JavaScript provides with classes, and how inheritance works.

Working With Classes

Here’s how you define a basic class MyClass, and create an instance of MyClass.

class MyClass {
  constructor() {
    this.answer = 42;
  }
}

const obj = new MyClass();
obj.answer; // 42

You must instantiate a class with new. Calling MyClass() without new throws an error:

// TypeError: Class constructor MyClass cannot be invoked without 'new'
MyClass();

A class is technically a function, although the ECMAScript spec explicitly disallows calling a class without new. In fact, the typeof operator identifies MyClass as a function.

typeof MyClass; // 'function'
MyClass instanceof Function; //  true

To check whether an object is an instance of a class, you should use the instanceof operator. You can also check whether the constructor property is equal to MyClass.

obj instanceof MyClass; // true
// Works, but `instanceof` is better...
obj.constructor === MyClass;

// Because `instanceof` is immune to overwriting the `constructor` property
const obj = {};
obj.constructor = MyClass;
obj instanceof MyClass; // false
obj.constructor === MyClass; // true

Like functions, classes in JavaScript are variables like any other. You can assign a class to a variable, overwrite that class, and pass a class as a parameter to a function. Like functions, you can also declare classes with or without explicit names.

let Foo = class {
  constructor() {
    this.answer = 42;
  }
}

Foo = class {
  constructor() {
    this.answer = 43;
  }
}

console.log(Foo); // '[Function: Foo]'
console.log(new Foo()); // 'Foo { answer: 43 }'

Unlike functions, classes are never hoisted. In the below example the function Foo() prints successfully, because JavaScript looks ahead and ‘hoists’ Foo() to the top of the function. But trying to print the class Bar throws a reference error, because JavaScript does not hoist class definitions.

#es6 #javascript #web-development #programming #developer