Javascript object options: function or null

This question has probably been asked before, but I don't really know the proper keywords to find a solution on Google, so all my researches returned 0 :) Or better, all my researches ended up with "optional parameters" but for functions.

0

Let's assume I have this class:

var Class = function (params)
// I get the data somehow
params.name(data);



The problem is that not every time I instantiate new Class() I need also to set name() like:

new Class()

name()

new Class(
name: function (data)
// Do something with the data

... other params ...
)


But, with the above syntax, if I don't declare name parameter as a function, an error params.name is not a function is thrown:

params.name is not a function

// Error
new Class(
... other params ...
)


My question is: is there a way to set params.name() as an optional parameter (in the object) that can be a function or completely not exist (e.g. null)? Something like saying: "when you instantiate the class:

params.name()

null

name: function (data)

params.name(data)

name

3 Answers
3

In ES6, You can use default function parameter option, like

var Class = function(params =
name: (x) => x
)
// I get the data somehow
data='value';
params.name(data);


Class();
Class(name: x => console.log(x));

Hope this will help!

EDIT

Yes @brigo, you are right, sorry I overlooked that point. We are actually looking for nested default rather. A possible solution could be to destructure the object inside the function like

var Class = function(params = )
// I get the data somehow
data = 'value';
withDefaultParams =
name: (x) => x,
...params

withDefaultParams.name(data);


Class();
Class(
name: x => console.log('non-default')
);
Class(
others: x => console.log('non-default')
);

name

params

undefined

Class()

params.name is not a function

yes, you could do something like

if (typeof param.name === 'function')
param.name(data);
else
// dont do anything or do something different



If using jQuery is an option, you could use its extend method (API docs) like in the following example:

extend

var Class = function(params)

var _defaults =
name: function(),
some: 'other stuff'
;

params = jQuery.extend(_defaults,params);

// I get the data somehow
data='value';
params.name(data);


Class();
Class(foo:'bar');
Class(name: console.log );


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