Question

I try to set a default value for a given class property.

class MyClass
    name: (name = 'value') ->

The code above doesn’t return value. It returns the whole function.

a = new MyClass
a.name
> function (name) {
if (name == null) name = 'value';
} 

If I set a value to it then it works:

a = new MyClass
a.name = 'something'
a.name
> 'something' 

I’m wondering what would be the proper way to set a default value for a Class property in CoffeScript.

Answer 1

This:

class MyClass
    name: (name = 'value') ->

simply defines name as a method which takes one parameter, also called name, and the default value for that parameter is 'value'. So, if we add a body and execute the method:

class MyClass
    name: (name = 'value') ->
        console.log(name)
new MyClass().name()
new MyClass().name('pancakes')

You’ll see 'value' and 'pancakes' in the console. Here’s a demo, open your console to see what happens.

If you want instances of MyClass to have a name property whose default value is 'value' then you want to say this:

class MyClass
    constructor: (@name = 'value')
console.log(new MyClass().name)
console.log(new MyClass('pancakes').name)

That will also give you 'value' and 'pancakes' in the console.