model_vs_helper.js - Favor for Model class than helper function because helper naming going to be redundant, expose internal structure(violate encapsulation

model_vs_helper.js

// Model class approach

class UserModel {
    constructor(data) {
      this.data = data;
    }
  
    getSecondaryAddress() {
      this.data.address.filter(address => address.secondary);
    }
    
    static async fetchUserBy(){
        // some api call
        const result = {}
        return new UserModel(result)
    }
  }
  
  var user = await UserModel.fetchUserBy()
  console.log(user.getSecondaryAddress())
  
  
  // Helper approach
  
  //Helper.js
  
  export async fetchUserBy(){
      const result = {}
      return new UserModel(result)
  }
  
  export function getUserSecondaryAddress(address){
      return address.filter(address => address.secondary);
  }
  
  
  var user = await fetchUserBy()
  console.log(getSecondaryAddress(user.address))