Modules &

Design Patterns

What is a Module?

Sections of code which can be moved, removed or added without disrupting the system as a whole (keeps code organized and separated)

The benefits of using modules

  • Maintainability - Lessens the dependency on other parts of the codebase

  • Namespacing - Unrelated code shares global variables

  • Reusability - Ability to reuse modules

How to use modules?

  • By using a the module pattern which is a design pattern.
  • A design pattern is used to describe a common approach to solving a programming task.
  • The module pattern is a popular way to write code that contains both public and private logic

 

 

IIFE

 

  • An IIFE runs as soon as it is defined
  • The function is executed once as the interpreter comes across them
  • Used for code that only needs to run one within a task
  • Commonly used as a wrapper around a set of code

 

 

Module patterns uses an IFFE (Immediately Invoked Function Expression) to return an object

Anonymous Closure


(function(){
  
  //salaries are private
  var salaries = [1000, 2000, 5000, 7000, 10000];
  
  var avgSalary = function(){
    var total = 0;
    for(var i = 0; i<salaries.length; i++){
      total += salaries[i];
      var avg = total/salaries.length;
    }
    return avg;
  }
  
 console.log(avgSalary()); //5000
  
}());
  • Hides variables (local) from the global scope
  • A closure is where an inner function has access to the outer
  • Enclosing function's variables

The Object Interface

var workerSalaries = (function(){
  var salaries = [10, 20, 30, 40, 50];
  
  return {
    median: 30,
    maxSalary: function(){
      var max = Math.max(salaries[0], salaries[4]);
      return max;
  }
  }
    
}()); //50
  • Self contained object
  • The variable is kept private inside the closure scope
  • returns an object that can be accessed 

The Module Pattern

var openBank = (function(){
  //private
  var name = 'Jon Smith';
  var acctNo = 12345;
  var obj = {};
  
  
  //public var
  obj.balance = 300000;
  
  
  //public method
  obj.deposit = function(n){
    var newBal = this.balance + n;
    return newBal
  }
  
  return obj;
}())

console.log(openBank.balance)
console.log(openBank.deposit(1))
console.log(openBank.acctNo)
  • Create the object to be returned

The Revealing Module Pattern

var workerSalaries = (function(){
  var salaries = [10, 20, 30, 40, 50];
  
  var maxSalary = function(){
      var max = Math.max(salaries[0], salaries[4]);
      return max;
  }
  
  return {
    maxSalary: maxSalary
  }
    
}())

console.log(workerSalaries.maxSalary()) //50
  • Ensures that all variables and methods are kept private
  • Must be explicitly exposed to the public in the return object
  • Most popular of all the module patterns

Modules

By vic_lee

Made with Slides.com

Modules

  • 465

More from vic_lee