Delegation design pattern

delegation-pattern.js

// #### Delegation

// A SOLID method is delegated via composition. 

/**
 *
 */
type Subtask: Function(name: String): Function

/**
 *
 */
type Delegator: Function(task: Subtask): Function

( function() {

  let prop = 'value'

   // expressions
   let fn1: Subtask = function(
       name: String
    ): Function {
    
        return function(prefix: String) {
            return `${prefix}-${prop}`
        }
    }
   
   let fn2: Delegator = function(
       task: Subtask
   ): Function {
      
       return function(...args) {
       
           // other work
           // ...
                          
           // delegation
           task.apply(this, args)
       
       }
   }
  
} )( )