About

This module is based on this Stack Overflow Answer. It however includes a few changes to help extend classes with the ability to add prefixes or suffixes to the property names.

The purpose is to provide for a straight forward way to extend any class with a multiple other classes.

const extender=require("multi-extender);

// This base class can have some methods and properties accessible in all Extension Classes
class BaseClass {}

// the multiple classes we want to extend BaseClass with
class ExtensionOne {}
class ExtensionTwo {}

const MyBaseClass = extender(ExtensionOne, ExtensionTwo)(BaseClass);

Prefixes & Suffixes

Sometimes you want to extend multiple classes, say ( ExtClassA & ExtClassB ), but ExtClassA & ExtClassB have properties with similar names which means the properties of ExtClassA get overwritten by ExtClassB, which is definitely not what you wish.

This is where you use prefixes and suffixes.

To declare a prefix/suffix, we use the private class features notation so that the prefix/suffix declaration is localized and private to the class.

• To prefix we add the property #__prefix="your_prefix".
• To suffix we add the property #__suffix="your_prefix".

Below is an example:

const extender = require('multi-extender');

// This is our base class
class Base {
	one() {
        return 'Base Method one'
    }
}

// Below are the classes we want to extend Base with
// ExtendOne uses a prefix
// ExtendTwo uses a suffix
// Both have methods named "one" and "two"

class ExtendOne {
	#__prefix = 'prefix_';

	one() {
		return 'Extend one Method one';
	}
	two() {
		return 'Extend one Method two';
	}
}

class ExtendTwo {
	#__suffix = '_suffix';

	one() {
		return 'Extend two Method one';
	}

	two() {
		return 'Extend two Method two';
	}

	three() {
		return 'Extend two Method three';
	}
}

// Tet us apply the extension
let Extended = extender(ExtendOne, ExtendTwo)(Base);

// Now let us test and see how the extensions have been done

// 1. Initialize the class
let Initialized = new Extended();

// 2. Pick all property names
var propertyNames = Object.getOwnPropertyNames(Extended.prototype);
// 3 Loop through each property with exception of 'constructor'
let propReturns = propertyNames
	.filter((n) => n !== 'constructor')
	.map((name) => {
		//4. call each method and get return value
		return { prop: name, return: Initialized[name]() };
	});

// log results
console.log(propReturns);

This code will log the following

[
  { prop: 'one', return: 'Base Method one' },
  { prop: 'prefix_one', return: 'Extend one Method one' },
  { prop: 'prefix_two', return: 'Extend one Method two' },
  { prop: 'one_suffix', return: 'Extend two Method one' },
  { prop: 'two_suffix', return: 'Extend two Method two' },
  { prop: 'three_suffix', return: 'Extend two Method three' }
]

This shows that all six methods exist and have been appropriately renamed.

You can check out these examples in the test directory.

Important to Note:

• When you prefix or suffix classes, the methods will be renamed to "prefix" + "property" or "property" + "suffix". Therefore, if the prefix is declared as #__prefix="cls1_, then the method prop_one becomes cls1_prop_one and prop_one no longer exists!
• Therefore, you must select proper prefix/suffix names, cognizant of the fact that you will need to easily access the renamed properties. So name your prefixes and suffixes as you would name variables i.e.
  • Use snake or camel case
  • Avoid symbols or exclamations.