Javascript using this.function results in 'has no method' error

Question

I have this simple Javascript object that calls its own prototype method in one of its local methods. [SEE MY EDIT]

var Obj = function() {
    function inner() {
        this.exported();
    }

    this.exported = function() {
        alert("yay!");
    };
};

var test = new Obj();
Obj.exported();

However, I get the error TypeError: Object function() {...} has no method 'exported'. Any idea how this should be done?

EDIT: whoops, just realized I never called inner(), but thanks Patrick for answering that part anyways. Here is a better example

var Obj = function() {

    this.exported = function() {
        inner();
    };

    function inner() {
        this.yay();
    }

    this.yay = function() {
        alert("yay!");
    };
};

var test = new Obj();
test.exported();

I get TypeError: Object [object global] has no method 'exported'

There are no any prototype functions in your code btw.

zerkms
– zerkms

2014-03-15 21:31:03 +00:00
Commented Mar 15, 2014 at 21:31 — zerkms
– zerkms, Commented Mar 15, 2014 at 21:31

Suman Bogati · Accepted Answer · 2014-03-15 22:02:35Z

3

should be used

test.exported();

instead of

Obj.exported();

You should invoked exported() method over the test object, not over the Obj constructor.

UPDATE

After reached inside the function inner(){...}. this is refers to global window not Obj, so pass the actual object this from inner(this) and do invoke export() from that passed object into function inner(cthis){...}, something like.

function inner(cthis) {
    //----------^--get Obj on here
    cthis.exported();
}

this.exported2 = function() {
    inner(this);
   //------^--pass Obj from here
};

DEMO

edited Mar 15, 2014 at 22:02

answered Mar 15, 2014 at 21:30

Suman Bogati

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Comments

Patrick Evans · Accepted Answer · 2014-03-15 21:51:48Z

2

to call exported you need to call it off the variable you assigned the instance to:

test.exported();

Also for the inner function you cannot use this there to access the Obj object as it refers to window. save a reference to this and then use that to call the function

var Obj = function() {
    var _this = this;
    function inner() {
        _this.exported();
    }

    this.exported = function() {
        alert("yay!");
    };
};

edited Mar 15, 2014 at 21:51

answered Mar 15, 2014 at 21:30

Patrick Evans

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6 Comments

Kaii Over a year ago

true - but this has nothing to do with the question. inner() isn't called anywhere.

woojoo666 Over a year ago

but according to this answer the this refers to the top level object

woojoo666 Over a year ago

ok I think I get it now, this refers to the object prototype, not the current instance of the object?

Patrick Evans Over a year ago

@woojoo666, actually it refers to the global object, but that means it is window not Obj. Look at point 3 in that answer, when a function is executed without a context this refers to window. And since you have to execute inner without a context, ie inner();, so this will be window.

HMR Over a year ago

@woojoo666 the function called inner is available on a special scope called closure: developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Closures This is sometimes used to simulate private members. As zerkms pointed out; you're not using prototype and the disadvantage of simulating instance specific private members is that the functions that need to access them can't be put on the prototype. More information about prototype here: stackoverflow.com/a/16063711/1641941

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