Variations in the module pattern in JavaScript

Question

Variations in the module pattern in JavaScript

Can someone help me understand the differences in these methods of creating a javascript "module"? I'm just looking for some clarification.

A)

var foo = function() {
    var bar = function() {
        console.log('test');
    };

    return {
        bar: bar
    };
};

B)

var foo = function() {
    function bar() {
        console.log('test');
    };

    return {
        bar: bar
    };
};

C)

var foo = function() {
    this.bar = function() {
        console.log('test');
    };

    return {    
        bar: this.bar
    };
};

javascript module

Answer 1

Answer №1

Although A and B may seem identical, there exists a subtle difference between the two due to function/variable hoisting. In theory, it is possible to write code that works in B but fails in A; however, in practical terms, one would need to purposefully craft unconventional code to achieve this outcome.

C, while functional, deviates conceptually from best practices. The use of this.funcName within a function typically suggests constructor usage for creating numerous objects with new Thing(). If the intention is not to construct objects, using this style could mislead others into thinking otherwise, mistaking the function as a constructor instead of its true purpose as a module.

Answer 2

Although A and B may seem identical, there exists a subtle difference between the two due to function/variable hoisting. In theory, it is possible to write code that works in B but fails in A; however, in practical terms, one would need to purposefully craft unconventional code to achieve this outcome.

C, while functional, deviates conceptually from best practices. The use of this.funcName within a function typically suggests constructor usage for creating numerous objects with new Thing(). If the intention is not to construct objects, using this style could mislead others into thinking otherwise, mistaking the function as a constructor instead of its true purpose as a module.

Answer 3

Answer №2

Initially, you overlooked executing the function expression: the module pattern is an IEFE. You simply create a function.

The final example appears illogical, resembling a constructor function when assigning properties to this - and when executed as an IEFE it malfunctions (and using it with new produces unwanted effects; and returning an object renders it pointless).

To understand the distinction between the first and second code snippets, refer to var functionName = function() {} vs function functionName() {}. In the context of the module pattern, it is advisable to use function declaration.

Answer 4

Initially, you overlooked executing the function expression: the module pattern is an IEFE. You simply create a function.

The final example appears illogical, resembling a constructor function when assigning properties to this - and when executed as an IEFE it malfunctions (and using it with new produces unwanted effects; and returning an object renders it pointless).

To understand the distinction between the first and second code snippets, refer to var functionName = function() {} vs function functionName() {}. In the context of the module pattern, it is advisable to use function declaration.

Answer 5

Answer №3

//JavaScript Design Pattern
var company = (function() {
  var cname = 'CheapFlight';
  return {
   name: "Santosh Thakur",
   getAge: function() {
    return cname;
   },
   growOlder: function() {
    return cname + " Updated";
 }
 };
}());
company.cname = "New Business"
console.log(company.cname);
console.log(company.name);
console.log(company.getAge());
console.log(company.growOlder());

Answer 6

//JavaScript Design Pattern
var company = (function() {
  var cname = 'CheapFlight';
  return {
   name: "Santosh Thakur",
   getAge: function() {
    return cname;
   },
   growOlder: function() {
    return cname + " Updated";
 }
 };
}());
company.cname = "New Business"
console.log(company.cname);
console.log(company.name);
console.log(company.getAge());
console.log(company.growOlder());

Answer 7

Answer №4

Using the prefix 'var' before a function transforms it into something akin to a class, allowing for the creation of multiple versions. This concept applies to A.

For instance:

  var hi = function()
  {
    var bye = function()
    {
        alert("bye");
    }   
    bye(); // calling bye
    var something = new bye(); // creating a new instance of bye();
  }

  var something = new hi();
  something();

In B's case, you can only invoke bar, without generating a new instance within the function itself.

C behaves similarly to bar due to its scope.

Class-like behavior:

var Dog = function( hair, type )
{
     this.hair = hair;
     this.type = type;
}

var fred = new Dog( "long", "Dalmation" );
alert( fred.hair );    

var dave = new Dog( "short", "Poodle" );
alert( dave.type);

This represents a class ^

Answer 8

Using the prefix 'var' before a function transforms it into something akin to a class, allowing for the creation of multiple versions. This concept applies to A.

For instance:

  var hi = function()
  {
    var bye = function()
    {
        alert("bye");
    }   
    bye(); // calling bye
    var something = new bye(); // creating a new instance of bye();
  }

  var something = new hi();
  something();

In B's case, you can only invoke bar, without generating a new instance within the function itself.

C behaves similarly to bar due to its scope.

Class-like behavior:

var Dog = function( hair, type )
{
     this.hair = hair;
     this.type = type;
}

var fred = new Dog( "long", "Dalmation" );
alert( fred.hair );    

var dave = new Dog( "short", "Poodle" );
alert( dave.type);

This represents a class ^

Variations in the module pattern in JavaScript

Answer №1

Answer №2

Answer №3

Answer №4

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