refactor from aggregation repo

.eslintrc.js

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+module.exports = {
+  "ecmaFeatures": {
+    "modules": true,
+    "spread" : true,
+    "restParams" : true
+  },
+  // "plugins": [
+  // "unicorn"
+  //  ],
+  "env": {
+    "es6": true,
+    "node": true,
+    "mocha": true
+  },
+  "parserOptions": {
+    "ecmaVersion": 2017,
+    "sourceType": "module"
+  },
+  "extends": "eslint:recommended",
+  "rules": {
+    "indent": [
+      "error",
+      2
+    ],
+    // "unicorn/no-array-instanceof": "error",
+    "no-console": 0,
+    "semi": ["error", "never"],
+    "linebreak-style": [
+      "error",
+      "unix"
+    ],
+    "quotes": [
+      "error",
+      "single"
+    ]
+  }
+}

.gitignore

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+node_modules

.npmignore

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+tests/
+test/
+*.test.js
+testing/

README.md

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+
+Class Merge
+===========
+
+Merge of additional (mixin) Classes into an primary (base) class
+
+
+About
+-----
+
+Class Merge is a very small JavaScript library for Node.js environments,
+providing just a single function for use in ECMAScript 6 class
+inheritance. It aggregates/merges a base class and one or
+more mixin classes into an aggregate class, which then is usually
+subsequently used as the base class for another class.
+
+Installation
+------------
+
+```shell
+$ npm install @uci-utils/class-merge
+```
+
+
+Usage
+-----
+
+#### ECMAScript 6
+
+requires using -r esm
+
+```js
+import merge from '@uci-utils/class-merge'
+
+class Colored {
+    initializer ()     { this._color = "white" }
+    get color ()       { return this._color }
+    set color (v)      { this._color = v }
+}
+
+class ZCoord {
+    initializer ()     { this._z = 0 }
+    get z ()           { return this._z }
+    set z (v)          { this._z = v }
+}
+
+class Shape {
+    constructor (x, y) { this._x = x; this._y = y }
+    get x ()           { return this._x }
+    set x (v)          { this._x = v }
+    get y ()           { return this._y }
+    set y (v)          { this._y = v }
+}
+
+class Rectangle extends merge(Shape, Colored, ZCoord) {}
+
+var rect = new Rectangle(7, 42)
+rect.z     = 1000
+rect.color = "red"
+
+
+Credits
+-------
+
+aggregation 2015-2019  by Dr. Ralf S. Engelschall (http://engelschall.com/)

package.json

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+{
+  "name": "@uci-utils/class-merge",
+  "version": "1.0.1",
+  "description": "Function to merge classes when making an extended class",
+  "main": "src/merge.js",
+  "scripts": {
+    "test": "./node_modules/.bin/mocha -r esm --timeout 30000",
+    "testd": "UCI_ENV=dev ./node_modules/.bin/nodemon --exec './node_modules/.bin/mocha -r esm --timeout 30000' || exit 0"
+  },
+  "author": "David Kebler",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/uCOMmandIt/uci-utils-class-merge.git"
+  },
+  "keywords": [
+    "node.js",
+    "class",
+    "ES6",
+    "merge",
+    "extend"
+  ],
+  "bugs": {
+    "url": "https://github.com/uCOMmandIt/uci-utils-class-merge/issues"
+  },
+  "homepage": "https://github.com/uCOMmandIt/uci-utils/class-merge#readme",
+  "devDependencies": {
+    "chai": "^4.2.0",
+    "esm": "^3.2.25",
+    "mocha": "^7.0.1",
+    "nodemon": "^2.0.2"
+  }
+}

src/merge.js

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+
+/*  ==== ECMAScript 6 variant ====  */
+
+export default (base, ...mixins) => {
+
+  /*  create aggregation class  */
+  const merge = class __Merge extends base {
+    constructor (...args) {
+      /*  call base class constructor  */
+      super(...args)
+
+      /*  call mixin's initializer  */
+      mixins.forEach((mixin) => {
+        if (typeof mixin.prototype.initializer === 'function')
+          mixin.prototype.initializer.apply(this, args)
+      })
+    }
+  }
+
+  /*  copy properties  */
+  let copyProps = (target, source) => {
+    Reflect.ownKeys(source)
+      .forEach((prop) => {
+        if (typeof prop.match ==='function') {
+          if (prop.match(/^(?:initializer|constructor|prototype|arguments|caller|name|bind|call|apply|toString|length)$/))
+            return
+        }
+        Reflect.set(target,prop,Reflect.getOwnPropertyDescriptor(source, prop))
+      })
+  }
+
+  /*  copy all properties of all mixins into aggregation class  */
+  mixins.forEach((mixin) => {
+    copyProps(merge.prototype, mixin.prototype)
+    copyProps(merge, mixin)
+  })
+
+  return merge
+}

test/merge.js

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+import merge from '../src/merge.js'
+import { expect }  from 'chai'
+
+
+describe('Class Merge', function () {
+
+  class Colored {
+    initializer ()     { this._color = 'white' }
+    get color ()       { return this._color }
+    set color (v)      { this._color = v }
+  }
+
+  class ZCoord {
+    initializer ()     { this._z = 0 }
+    get z ()           { return this._z }
+    set z (v)          { this._z = v }
+  }
+
+  class Shape {
+    constructor (x, y) { this._x = x; this._y = y }
+    get x ()           { return this._x }
+    set x (v)          { this._x = v }
+    get y ()           { return this._y }
+    set y (v)          { this._y = v }
+  }
+
+  var Rectangle = class Rectangle extends merge(Shape, Colored, ZCoord) {}
+
+  var rect = new Rectangle(7, 42)
+  rect.z     = 1000
+  rect.color = 'red'
+
+
+  it('Should merge three classes', function () {
+    expect(rect.x).to.be.equal(7)
+    expect(rect.y).to.be.equal(42)
+    expect(rect.z).to.be.equal(1000)
+    expect(rect.color).to.be.equal('red')
+  })
+
+})