Call javascript class method from another method

Question

I have problem calling one method from another method in a Javascript class.

Here is the code

    function Spinner( max_value , min_value , div_id ){

    var MAX_VALUE = 25;
    var MIN_VALUE = -25;
    var DEFAULT_VALUE = 0;


    this.maxValue = max_value;
    this.minValue = min_value;
    this.divId    = div_id;
    this.spinnerControl; //spinner control object that is populated in getSpinner() method.


    this.rotateSpinner = function (spinnerTextBoxId,up) {

        document.getElementById(spinnerTextBoxId).value = up ? parseInt(document
                .getElementById(spinnerTextBoxId).value) + 1 : parseInt(document
                .getElementById(spinnerTextBoxId).value) - 1;
    };


    this.getSpinner = function( ){

        spinnerControl = $('<input type="text"></input>')
                .attr('id' , 'spinner')
                .attr('val' , DEFAULT_VALUE)
                    .add( $('<ul></ul>')
                        .addClass("spinner")
                        .append(
                            $('<li></li>')
                            .append($('<input type="button"></input>') 
                                .attr({
                                    id    : 'upButton',
                                    value : '&#9650;'
                                }).appendTo( $('<li></li>') )
                            )   


                        ).append( $('<li></li>')
                            .append($('<input type="button"></input>') 
                                    .attr({
                                        id    : 'downButton',
                                        value : '&#9660;'
                                    }).appendTo( $('<li></li>') )
                            )
                        )   

                    );

            var timeoutId = 0;
            $('#upButton' , spinnerControl).mousedown(function() {
                console.log('mouse down');
                timeoutId = setInterval(this.rotateSpinner('spinner' , true ) , 200);
            }).bind('mouseup mouseleave', function() {
                console.log('mouse left');
                //clearTimeout(timeoutId);
            });


//      $('#downButton').mousedown(function() {
//          alert('herer');
//          //timeoutId = setInterval("rotateSpinner('spinner' , false ) ", 200);
//      }).bind('mouseup mouseleave', function() {
//          clearTimeout(timeoutId);
//      });

        return spinnerControl;
    };







//class END 
}

In this js file ,the error shows up in firebug : "Reference error : rotateSpinner" is not defined.

Why is it appearing ?

I had already seen the post but haven't figure out the problem yet, rotateSpinner is not called. I haven't used new operator as suggested in that question. — Taha Iqbal
– Taha Iqbal, Commented Jul 8, 2013 at 6:21
try to define rotateSpinner variable to outside of function as a gloabl variable. — Devang Rathod
– Devang Rathod, Commented Jul 8, 2013 at 6:27

Adam · Accepted Answer · 2013-07-08 06:29:54Z

this is referring the DOM-element, which in this case is the '#upButton'. If you add a variable that points to the class, you can then refer to this one instead of this when defining functions within the method.

function Spinner( max_value , min_value , div_id ){

var MAX_VALUE = 25;
var MIN_VALUE = -25;
var DEFAULT_VALUE = 0;


this.maxValue = max_value;
this.minValue = min_value;
this.divId    = div_id;
this.spinnerControl; //spinner control object that is populated in getSpinner() method.


this.rotateSpinner = function (spinnerTextBoxId,up) {

    document.getElementById(spinnerTextBoxId).value = up ? parseInt(document
            .getElementById(spinnerTextBoxId).value) + 1 : parseInt(document
            .getElementById(spinnerTextBoxId).value) - 1;
};


this.getSpinner = function( ){
    var self = this;
    spinnerControl = $('<input type="text"></input>')
            .attr('id' , 'spinner')
            .attr('val' , DEFAULT_VALUE)
                .add( $('<ul></ul>')
                    .addClass("spinner")
                    .append(
                        $('<li></li>')
                        .append($('<input type="button"></input>') 
                            .attr({
                                id    : 'upButton',
                                value : '&#9650;'
                            }).appendTo( $('<li></li>') )
                        )   


                    ).append( $('<li></li>')
                        .append($('<input type="button"></input>') 
                                .attr({
                                    id    : 'downButton',
                                    value : '&#9660;'
                                }).appendTo( $('<li></li>') )
                        )
                    )   

                );

        var timeoutId = 0;
        $('#upButton' , spinnerControl).mousedown(function() {
            console.log('mouse down');
            timeoutId = setInterval(self.rotateSpinner('spinner' , true ) , 200);
        }).bind('mouseup mouseleave', function() {
            console.log('mouse left');
            //clearTimeout(timeoutId);
        });


//      $('#downButton').mousedown(function() {
//          alert('herer');
//          //timeoutId = setInterval("rotateSpinner('spinner' , false ) ", 200);
//      }).bind('mouseup mouseleave', function() {
//          clearTimeout(timeoutId);
//      });

    return spinnerControl;
};







//class END 
}

Agree with this :). One best practice is that we can assign a variable var that = this.

Howard · Accepted Answer · 2013-07-08 06:25:58Z

1

Depends on how you call this function.

If you call it like this:

Spinner().rotateSpinner(arg1, arg2);

You would the error you mentioned.

The right usage is:

new Spinner().rotateSpinner(arg1, arg2);

It's better you learn more about variable scope of javascript.

answered Jul 8, 2013 at 6:25

Howard

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3 Comments

Taha Iqbal Over a year ago

It worked with new Spinner().rotateSpinner(,) approach. So it means there is not concept of private methods or calling methods from inside methods in javascript ?? I think of it is simply a method declared and call it from another method. But getting it called from object reference is strange to me .

Adam Over a year ago

@TahaIqbal Yes, you can call other methods from other methods. But in your case you are calling the method of a dom-element and not your class. Look at my answer below

Howard Over a year ago

It is about who the caller is!? If you call it like "Spinner().rotateSpinner(arg1, arg2);", which means the caller is "window", so the script engine tries to find "rotateSpinner" in global env, obviously there isn't such a method in it. Then error occurs.

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