Can anyone tell me if the following example classes are equivalent, with respect to the class properties. One is defined within the constuctor and one outside.

Example 1

function Test(input)
{
    this.output = input ;
    Test.WELCOME = "Hello ;
}

Example 2

function Test(input)
{
    this.output = input ;        
}

Test.WELCOME = "Hello ;

I have been using the second type but both seems to work.

Cheers

Can anyone tell me if the following example classes are equivalent, with respect to the class properties. One is defined within the constuctor and one outside.

Example 1

function Test(input)
{
    this.output = input ;
    Test.WELCOME = "Hello ;
}

Example 2

function Test(input)
{
    this.output = input ;        
}

Test.WELCOME = "Hello ;

I have been using the second type but both seems to work.

Cheers

• javascript

• Related: Class keyword in Javascript. Zoso - Where is this JavaScript running? (probably not a browser) – Kobi Commented Nov 30, 2011 at 11:28
• unless you are in some very early ES.Next alpha engine, there is no used class keyword in javascript. – jAndy Commented Nov 30, 2011 at 11:28
• sorry mistyped class should have been function. These are simulated classes not true class. – ZosoOfZep Commented Nov 30, 2011 at 11:32
• 1 @Kobi Ahh, interesting! Cool. – Pekka Commented Nov 30, 2011 at 11:35

2 Answers 2

I'm pretty sure neither of those does what you really want it to do. The usual way this inside of Test is something useful will be when instantiating it using new. Setting a property on Test itself doesn't have any effect on objects created from it using x = new Test('someinput'). What you would want to do is Test.prototype.WELCOME = 'Hello' and instances of Test would have that property in their [[proto]] tree and then be able to make use of it.

function Test(input){
  this.output = input;
}
Test.prototype.WELCOME = 'Hello';

var instanceOfTest = new Test('whatever');

// produces this structure:
instanceOfTest => {
  output: 'whatever',
  __proto__: {
    WELCOME: 'Hello'
  }
}

console.log(instanceOfTest.WELCOME); // 'Hello'

Assuming you mean:

function Test(input)
{
  this.output = input;
  Test.WELCOME = "Hello";
}

Example 2

function Test(input)
{
  this.output = input ;        
}
Test.WELCOME = "Hello";

Then there will be no difference in terms of the properties of any new Test objects, however in Example 1 you will be assigning a WELCOME property to the Test function on each call to the method, whereas in Example 2 you will only assign this property once.