scope issue with function call from object

Question

I need to execute the fc.text-function via fc.messages.max.call( this );

But I do have the error: TypeError: fc is undefined.

The pure fc.text-function works.

I need some explanation with the scopehandling.

Here is the Fiddle

Here is my Code

var fc = {

        methods: { },

        test: function(whatever) {
              console.log("test:", whatever);
            },
        messages: {
            tata: "hello", 
            max: fc.test("Geben Sie bitte einen Wert kleiner oder gleich {0} ein."),
            min: fc.test("Geben Sie bitte einen Wert größer oder gleich {0} ein."),
        },

        otherTest: function() {
                console.log("otherTest works"); 
                fc.test("otherTest");     
                }

   };

fc.test("hello world"); //works
fc.otherTest();         //works also

//fc.messages.max.call( this );

How can i fix this ?

I made another jsfiddle where it works fine. but the function is in a different scope. one more fiddle

Any explanation?

What do you want messages.max and messages.min to become? — Bergi
– Bergi, Commented Apr 7, 2014 at 12:04
This has nothing to do with the this context, you don't need to use .call — Bergi
– Bergi, Commented Apr 7, 2014 at 12:05

pstenstrm · Accepted Answer · 2014-04-07 12:00:55Z

1

The call() method is a property of of the Function object.

fc.messages.max isn't a function. It's value is the return value of fc.test(), which is undefined.

answered Apr 7, 2014 at 12:00

pstenstrm

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2 Comments

hamburger Over a year ago

If you have a look to my second jsfiddle, there it works. the only different is that the function is in an other scope. Why I can't call them like i did?

pstenstrm Over a year ago

You can't access fc from within fc. When you declare max: fc.test( fc wont exist yet, as JS need to compile the entire object before it sets the fc variable.

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

From the mdn docs:

The call() method calls a function with a given this value and arguments provided individually.

min: & max: were not functions so you could not call() them.

What calls what:

var test = function( t ) {
    console.log("one more test: ",t);
};
var fc = {
    
    methods: { },
    
    test: function(whatever) {
        console.log("test:", whatever);
    },
    messages: {
        tata: "hello", 
        max: function() { test("var test") },
        min: function() { fc.test("fc test") }
    },
    
    otherTest: function() {
        console.log("otherTest works"); 
        fc.test("otherTest");     
    }
    
};

fc.test("fc test, hello world"); //calls fc.test
test("var test, hello world"); // calls var test
// fc.otherTest();         //works also

fc.messages.max.call( this ); // call var test
fc.messages.min.call( this ); // calls fc.test

http://jsfiddle.net/v7xT6/7/

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Apr 7, 2014 at 12:05

Rick Lancee

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5 Comments

hamburger Over a year ago

thx but this is not what iam looking for. I made on your base another fiddle to demonstrate jsfiddle.net/v7xT6/3. this works fine. but the function is in another scope.

Rick Lancee Over a year ago

@hamburger jsfiddle.net/v7xT6/5 ? this calls the var test function. Which test function do you want to call the one inside fc, or the one outside?

Rick Lancee Over a year ago

@hamburger i've updated the answer to show what calls what heres the fiddle: jsfiddle.net/v7xT6/7

hamburger Over a year ago

thx Rick, I have seen it. In my second jsfiddle it works without declaring max as a function. I'am looking for an explanation, because I do not understand why?

Rick Lancee Over a year ago

@hamburger in your second fiddle you are not calling the max function, when you do call it it throws an undefined error, because its not a function.

phylax · Accepted Answer · 2014-04-07 12:01:40Z

0

Im not sure, but i think you can't access fc.test() because in messages fc is not complete yet.

compare:

var f = { a: function () { return 1; }, max: f.a() }
> TypeError: Cannot call method 'a' of undefined

It says f is undefined.

You can't access f until the assignment (var f) is complete and f is defined.

answered Apr 7, 2014 at 12:01

phylax

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