To start with, the main purpose of a method is not sharing code, it is to help us abstract parts of our code and give that code a more understandable label.

• Arrays or Functions
  • Return Array || Empty collection
  • For nested objects. Set values to Array || Empty Collection
• Objects
  • Use a null object that handles the null check
  • IBoss
    • Boss
    • NullBoss

• ❌Instead of using enums as
  • StatusEnum
    • Pending
    • PaymentRejected
    • Canceled
  • Order
    • Status : StatusEnum
    • PlaceOrder()
      • If(status === enu.status.Pending) {}
      • If(status === enu.status.PaymentRejected) {}
      • If(status === enu.status.Canceled) {}
• ✔Create a Class of each case
  • IOrder
    • PlaceOrder()
  • PendingOrder implements IOrder
  • PaymentRejectedOrder implements IOrder
  • CanceledOrder implements IOrder

• Combine
  • Assign a constant for each conditional
    • const isAdmin:boolean = user.role === "admin" etc...
    • if(isAdmin && isActive && canEdit)
  • Combine common conditionals to a single constant
    • if(activeAdminCanEdit)
• Extract to Class
  • Extract conditional logic on User Class
    • User.isActive()
    • User.canEdit()
• Extract to explicit Classes
  • Class UserIsActiveAdmin
• Pipe Classes
  • IPipeCondition
    • Check()
  • Class UserIsActiveAdmin implements IPipeCondition
  • Then create a collection of IPipeCondition(s) and a for loop to check() the conditions

• Fail fast
• Sort if clauses by which who will fail first
• Best used with Gate Classes

• For clauses that are considered gates for big code blocks
• Create classes that handle the if clause and the code blocks then throw an exception on failure

• ❌Instead of getting primitive values like
  • Const domain:string = email.replace(/.*@/,"");
  • const userName = email.replace(domain, "");
• ✔Create a class (Value Object) like
  • Email
    • Value
    • Domain = Value.replace(/.*@/,"");
    • Username = domain.replace(domain, "");

• ❌Instead of filling a User class with functions that will be used once like
  • User.isAuthenticated()
  • User.isActive()
  • User.alreadyHadSession()
  • User.isLockedOut()
  • User.isFirstLogin()
• ✔Change the isAuthenticated function to return an enum
  • AuthenticationResultenum
    • InvalidCredentials
    • UserIsNotActive
    • HasExistingSession
    • IsLockedOut
    • IsFirstLogin
    • Successful

• ❌Instead of method getUsers() with params like
  • IncludeInactive:boolean
  • FilterText:string
  • OrderByName:boolean
• ✔Make this method private and create a public method for each use like
  • GetActiveUsers()
    • Return getUsers(false)
  • GetInactiveUsers
    • Return getUsers(true)

• Create Enum
  • OrderStatusEnum
    • Pending
    • Shipped
    • Cancelled
• Create strategy
  • Const strategies: Function[] = []
• Push strategies
  • Strategies[OrderStatusEnum.Pending] = processPendingOrder
  • Strategies[OrderStatusEnum.Shipped] = processShippedOrder
  • Strategies[OrderStatusEnum.Cancelled] = processCancelledOrder
• Execute the appropriate strategy
  • Strategies[order.getStatus()]

• Must specify return type of a function
• If a function is to be used from different locations
  • Must be placed in a 🌟reachable🌟 Class
• If a function is a service, it should have its own try catch block
• If a method is longer than the screen, then it's probably too long