JS call function when calling object without method

Question

so I have an object Obj with some methods. If the object is called without any method I would like to run a specific method. Is that possible? If so how?

e.g.

function obj(variable){
    this.method = function(){};
    this.noMethod = function(){};
}
var test = new obj(variable);

Calling console.log(test) should now call noMethod on test. I hope you get what I mean.

The object has a nodelist if you call a method, it runs the method. If you just call the object it should return the nodelist and possible alter it, depending on the argument.

Is there maybe a way to check if the object is called with a method? This way I could have an if-Statement to check and run my method if no other method is called.

Perhaps u should look into proxies wiki.ecmascript.org/doku.php?id=harmony:direct_proxies — Comfortably Numb
– Comfortably Numb, Commented Feb 26, 2014 at 22:39
Hi Lukas, what's the background to your problem? Are you looking for a way to see detail in the console? — Alex KeySmith
– Alex KeySmith, Commented Feb 26, 2014 at 23:14
I should have explained more, the object has a nodelist. I want to either run a method or return the nodelist. — Lukas Oppermann
– Lukas Oppermann, Commented Feb 26, 2014 at 23:17
So executing the console.log(test) would execute a method if no nodelist existed? — Alex KeySmith
– Alex KeySmith, Commented Feb 26, 2014 at 23:22

Oriol · Accepted Answer · 2014-02-26 23:09:35Z

Note that the exact behavior you want is not possible (afaik), because

You want to call test.noMethod without converting test into string, nor making it a function calling it. That means you need a getter.
But if you add a getter to test, then test.otherMethod will call test.noMethod too!

Some alternatives:

Use .toString() method:

function Obj(variable){
    this.method = function(){};
    this.noMethod = function(){ alert('foo'); };
    this.toString = function(){ return this.noMethod(); }
}
var test = new Obj();
test+''; // Calls test.noMethod, and returns test.noMethod()

Use getters (1):

function Obj(variable){
    this.method = function(){};
    this.noMethod = function(){ alert('foo'); };
}
var obj = {test: new Obj()}, tmp = obj.test;
Object.defineProperty(obj, 'test', {
  get: function(){ return tmp.noMethod() }
});
obj.test; // Calls tmp.noMethod, and returns test.noMethod()
obj.test.noMethod(); // Calls test.noMethod once and throws an error!

Use getters (2):

function Obj(variable){
    this.method = function(){};
    this.noMethod = function(){ alert('foo'); };
}
var obj = {test: new Obj()}, tmp = obj.test;
Object.defineProperty(obj, 'test', {
  get: function(){ tmp.noMethod(); return tmp }
});
obj.test; // Calls tmp.noMethod, and returns tmp
obj.test.noMethod(); // Calls test.noMethod twice!

Use function:

function Obj(variable){
    var f = function(){ return f.noMethod(); };
    f.method = function(){};
    f.noMethod = function(){ alert('foo'); };
    return f;
}
var test = new Obj();
test(); // Calls test.noMethod, and returns test.noMethod()
test instanceof Obj // false!

mrpanda · Accepted Answer · 2014-02-26 23:27:00Z

1

have you looked into the arguments.length for javascript

function obj(variable, bool){
    if(bool)
     this.method = function(){}; 
    else
     this.noMethod = function(){};
}
var test = new obj(something, false);

calling console.log(test) should result in this.noMethod

edited Feb 26, 2014 at 23:27

answered Feb 26, 2014 at 22:40

mrpanda

1045 bronze badges

4 Comments

Mouseroot Over a year ago

your example is backwards, but valid.

Lukas Oppermann Over a year ago

I think this fails when doing new object('some value'); because it will not be 0.

mrpanda Over a year ago

@LukasOppermann if what I am understanding is correct then you should supply a optional bool. I understand this is a dumb way but it would get you what you need function(variable, bool){ if(bool) this.method else this.noMethod }

Oriol Over a year ago

console.log(test, false) logs test and false in the console, instead of calling test.noMethod()

Andrei B · Accepted Answer · 2014-02-26 22:43:06Z

0

You are looking for this

function obj(){
    this.method = function(){};
    this.noMethod = function(){};
    this.toString = function() {return 'x'}
}
var test = new obj();
alert(test)

or this:

function obj(){
    this.method = function(){};
    this.noMethod = function(){};
}
obj.prototype.toString = function() {return 'x'}
var test = new obj();
alert(test)

See more here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString

answered Feb 26, 2014 at 22:43

Andrei B

2,76219 silver badges12 bronze badges

2 Comments

Lukas Oppermann Over a year ago

But this only works if I need it in a string context. If I do console.log(test) it would not call toString, correct? (Thats what happened when I tried it)

Andrei B Over a year ago

Correct. Console.log is a beast of it's own. AFAIK, it iterates project properties vs just calling toString.

Mouseroot · Accepted Answer · 2014-02-26 22:44:32Z

0

This should call no method when used, and a method when called, if not then im not sure you can accomplish this without a function.

function Obj() {
  this.method = function(){};
  this.noMethod = function(){};
  return this.noMethod();
}

I originally said to use the arguments var but that still doesn't fit your request.

edited Feb 26, 2014 at 22:44

answered Feb 26, 2014 at 22:37

Mouseroot

1,0742 gold badges9 silver badges13 bronze badges

3 Comments

james emanon Over a year ago

problem with this, as I initially posted similiar - is that in his obj, he'll call the method and call the no method.. since test.method() is also calling the obj without args.

dsuess Over a year ago

using the "new" operator often refers to the "constructor design pattern" To avoid misunderstanding of the code style / convention, please take a short look at the constructor pattern at addyosmani.com/resources/essentialjsdesignpatterns/book/…

Lukas Oppermann Over a year ago

This would only work if I would never initialize obj with arguments, right? I need that too, adjusted above.

Alex KeySmith · Accepted Answer · 2014-02-26 23:47:06Z

0

From your comments on the question, this doesn't quite solve what you are after, I'm not sure if that's really possible, as I think your trying to execute a function without calling a function - which is sort of possible with constructor ideas - but again I don't think you're after that.

But this sort of structure might give you some ideas for alternatives (though admittedly it's not really what you are after).

var test = function() {
    alert('hello');

    return {
        moo : function() {
            alert('moo');
        }
    }
};

var obj = test(); //hello

obj.moo(); //moo

http://jsfiddle.net/6Vpfa/

EDIT:

Maybe it does help, happy days :-)

edited Feb 26, 2014 at 23:47

answered Feb 26, 2014 at 23:41

Alex KeySmith

17.2k11 gold badges83 silver badges160 bronze badges

4 Comments

Lukas Oppermann Over a year ago

Okay, it looks pretty much like it is exactly what I need, why are you saying it is not what I need?

Alex KeySmith Over a year ago

Cool! That's lucky! The reason I thought otherwise is that test() is sort of acting like a constructor and should only be executed once, as it'll return a new "moo function" each time. But you may be able to twist this to suit your needs.

Lukas Oppermann Over a year ago

Darn I think it does actually not work. Because if you need to return the nodelist you run into trouble, it only works with alert, because it invokes itself.

Alex KeySmith Over a year ago

Maybe a mixture of this an some magic "apply" stuff. But it may end up being counter intuitive when reading calling code as it's bending things quite a bit.

Collectives™ on Stack Overflow

JS call function when calling object without method

5 Answers 5

Comments

4 Comments

2 Comments

3 Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

4 Comments

2 Comments

3 Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related