Solutions to manage big classes through multiple files for modularity

base.js

export defaut MyBigClass extends MyParent {
  constructor() {
    super()
  }
  
  method1() {
    // ...
  }
  
  method2() {
    // Link to method1 in logic
  }
  
  method3() {
    // ...
  }
  
  method4() {
    // ...
  }
  
  // More big methods
}

call.js

export MyFragment1 {
  method1: () => {
    // ...
  },
  
  method2: () => {
    // Link to method1 in logic
  }
}

export MyFragment2 {
  method3: () => {
    // ...
  }
}

export MyFragment3 {
  method4: () => {
    // ...
  }
}

export defaut class MyBigClass extends MyParent {
  constructor() {
    super()
    const fragments = { ...MyFragment1, ...MyFragment2, ...MyFragment3 }
    Object.keys(fragments).forEach((k) => {
      this[k] = (...args) => fragments[k].call(this, ...args)
    })
  }
  
  // More big methods
}

call2.js

export class MyFragment1 {
  constructor(bigClass) {
    super()
    this.bigClass = bigClass
  }
  
  method1() {
    // ...
  }
  
  method2() {
    // Link to method1 in logic
  }
}

export class MyFragment2 {
  constructor(bigClass) {
    super()
    this.bigClass = bigClass
  }
  
  method3() {
    // ...
  }
}

export class MyFragment3 {
  constructor(bigClass) {
    super()
    this.bigClass = bigClass
  }
  
  method4() {
    // ...
  }
}

export defaut class MyBigClass extends MyParent {
  constructor() {
    super()
    MyFragment1.call(this)
    MyFragment2.call(this)
    MyFragment3.call(this)
  }
  
  // More big methods
}

object.js

export MyFragment1 (self) => {
  method1: () => {
    // ...
  },
  
  method2: () => {
    // Link to method1 in logic
  }
}

export MyFragment2 (self) => {
  method3: () => {
    // ...
  }
}

export MyFragment3 (self) =>  {
  method4: () => {
    // ...
  }
}

export defaut class MyBigClass extends MyParent {
  constructor() {
    super()
  }
  
  MyFragment1 = MyFragment1(this)
  MyFragment2 = MyFragment2(this)
  MyFragment3 = MyFragment3(this)
  
  // More big methods
}

reduce.js

export MyFragment1 = (Parent) => class MyFragment1 extends (Parent || Object) {
  constructor() {
    super()
  }
  
  method1() {
    // ...
  }
  
  method2() {
    // Link to method1 in logic
  }
}

export MyFragment2 = (Parent) => class MyFragment2 extends (Parent || Object) {
  constructor() {
    super()
  }
  
  method3() {
    // ...
  }
}

export MyFragment3 = (Parent) => class MyFragment3 extends (Parent || Object) {
  constructor() {
    super()
  }
  
  method4() {
    // ...
  }
}

export defaut class MyBigClass extends EXTENDED_MODELS.reduce((extended, model) => model(extended), MyParent) {
  constructor() {
    super()
  }
  
  // More big methods
}

subclass.js

export class MyFragment1 {
  constructor(bigClass) {
    super()
    this.bigClass = bigClass
  }
  
  method1() {
    // ...
  }
  
  method2() {
    // Link to method1 in logic
  }
}

export class MyFragment2 {
  constructor(bigClass) {
    super()
    this.bigClass = bigClass
  }
  
  method3() {
    // ...
  }
}

export class MyFragment3 {
  constructor(bigClass) {
    super()
    this.bigClass = bigClass
  }
  
  method4() {
    // ...
  }
}

export defaut class MyBigClass extends MyParent {
  constructor() {
    super()
  }
  
  MyFragment1 = MyFragment1(this)
  MyFragment2 = MyFragment2(this)
  MyFragment3 = MyFragment3(this)
  
  // More big methods
}