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  3. Node.js — Extend Multiple Classes (Multi Inheritance)

Node.js — Extend Multiple Classes (Multi Inheritance)

Node.js benefits from new language features in JavaScript. The introduction of classes in JavaScript is a great step towards better extensibility.

You provide functionality in a base class, let other classes extend this base class, and use the given methods.

But how to extend multiple classes in Node.js? Read on to see how that works!

Node.js Series Overview

  1. Increase the Memory Limit for Your Process
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  4. Create Your Own Custom Error
  5. Retrieve a Request’s IP Address in Node.js
  6. Detect the Node.js Version in a Running Process or App
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  8. Check if a Value Is Null or Undefined in JavaScript or Node.js
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  10. Fix „Socket Hang Up“ Errors
  11. Nested Destructuring in JavaScript or Node.js
  1. String Replace All Appearances
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  6. Get the Part Before a Character in a String in JavaScript or Node.js
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  8. How to Check if a Value is a String in JavaScript or Node.js
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  10. Check if a Value is a String in JavaScript and Node.js
  11. Limit and Truncate a String to a Given Length in JavaScript and Node.js
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  22. Get the Part Before Last Occurrence in a String in JavaScript or Node.js
  23. Get the Part After Last Occurrence in a String in JavaScript or Node.js
  24. How to Count Words in a File
  25. How to Shuffle the Characters of a String in JavaScript or Node.js
  26. Append Characters or Words to a String in JavaScript or Node.js
  27. Check if a String is Empty in JavaScript or Node.js
  28. Ensure a String Ends with a Given Character in JavaScript or Node.js
  29. Left-Trim Characters Off a String in JavaScript or Node.js
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  1. How to Run an Asynchronous Function in Array.map()
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  3. for…of vs. for…in Loops
  4. Clone/Copy an Array in JavaScript and Node.js
  5. Get an Array With Unique Values (Delete Duplicates)
  6. Sort an Array of Integers in JavaScript and Node.js
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  12. Split an Array Into Smaller Array Chunks in JavaScript and Node.js
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  7. Overview of Promise-Based APIs in Node.js
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  4. Securely Parse JSON
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  1. How to Merge Objects
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  1. How to Download a File
  2. Strict Type for Request Headers with TypeScript
  1. Calculate an MD5 Hash
  2. Retrieve the List of Supported Hash Algorithms
  3. Calculate a SHA256 Hash
  4. Calculate a SHA512 Hash

Install the “extends-classes” Package

By default, each class in Node.js can extend only a single class. That means, to inherit from multiple classes, you’d need to create a hierarchy of classes that extend each other.

But wait, there’s a simpler solution. The ts-mixer package provides a convenient feature to extend multiple classes at once. At first, install the package to your project:

npm i ts-mixer

Extend Multiple Classes

Now that you installed the ts-mixer package, go ahead and use it in your app.

The following code snippet is a preview of how Supercharge composes the base testing utility. Individual classes implement features like HTTP testing or faking data and the base test should extend all classes to make them available for the user.

const Many = require('ts-mixer')  
const RenderViews = require('./concerns/render-views')  
const FakeData = require('./concerns/creates-fake-data')  
const MakeHttpRequests = require('./concerns/makes-http-requests')

class BaseTest extends Many(RenderViews, FakeData, MakeHttpRequests) {  
  constructor () {
    super()

    this
      .methodFromRenderViews()
      .methodFromFakeData()
      .methodFromMakeHttpRequests()
  }
}

module.exports = BaseTest

Pass all classes as separate arguments to the import of extends-classes and it will do the inheritance. Notice that I’ve imported extends-classes as Many.

That’s it!

Enjoy coding & make it rock!

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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