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JavaScript

Posted by PoJung Chen
PoJung Chen
5,856 Points

Why need to pass an empty object in parameter of class constructor ?

I know we can use object destructuring in ES6. However, in the course, it set the parameter of constructor such as 

class Person {
  constructor ({firstname, lastname, country = 'Taiwan'} = {}) {
    ...
 }
}

in the parameter {firstname, lastname, country = 'Taiwan'} = {} why I need to pass it to an empty object? I found that I could write 

constructor ({firstname, lastname, country = 'Taiwan'} ) {
...
}

and it will return the same result.

So I am wondering why teacher always set the object to an empty object?

1 Answer

Steven Parker
Steven Parker
243,318 Points
Steven Parker
Steven Parker
243,318 Points

Giving the constructor an empty object default lets you to instantiate with no arguments.

With the default empty object as in your first example, you can then create a new instance without providing any arguments, like this :point_right: let Joe = new Person();

But if you have no default, as in your second example, that code would cause an error. You would then be required to provide an argument, even an empty one, for each instance you create.

PoJung Chen
PoJung Chen
5,856 Points

Got it! Thanks a lot!