Javascript: Why can not get variable in callback function?

Question

I've read several different callback function documentation but unfortunately couldn't be success to get related variable. What I'm missing on here?

checkNo: function (callback) {
    var comboQuery = Ext.ComponentQuery.query('[name=foocombo]')[0].getSelectedRecord();
    var chkno = comboQuery.get('mychkno'); //Success to get this integer value

    callback(chkno); //Error raises here. Debugger says "callback is not a function"
    //if (callback) callback(chkno); //I've tried to check callback but did not work as well.
},

setFooCombo: function () {
    var me = this;
    var fooStore = Ext.getStore('fooComboStore');
    var chkno = ''; //Trying to pass an empty value. Not sure if correct approach 
    var checkno = me.checkNo(chkno); //Trying to get returned value from above function to be able using on url.

    fooStore.getProxy().setUrl(MyApp.Url() + '/foo/list?=' + checkno); //I need pass value that return from callback to here
    if (typeof checkno === MyApp.NUMBER) {
        fooStore.load();
    }


    // I've tried another way to set new URL as below but did not work too.
    // me.checkNo(function (checkno) {
    //fooStore.getProxy().setUrl(MyApp.Url() + '/foo/list?=' + checkno);
    //     if (typeof checkno === MyApp.NUMBER) {
    //         fooStore.load();
    //     }
    // });
},

UPDATE: After Rahul Khandelwal's answer re-factored the functions and of course now works.

checkNo: function () {
    var comboQuery = Ext.ComponentQuery.query('[name=foocombo]')[0].getSelectedRecord();
    var chkno = comboQuery.get('checkno');

    return chkno;

},

setFooCombo: function () {
    var me = this;
    var fooStore = Ext.getStore('fooComboStore');
    var checkno = me.checkNo();

    fooStore.getProxy().setUrl(MyApp.Url() + '/foo/list?=' + checkno);
    if (typeof checkno === MyApp.NUMBER) {
        fooStore.load();
    }
},

also, `chkno` is defined in `setFooCombo` not in `checkNo` - and it is not a function so therefore `callback` is not a function' — Jaromanda X, May 08 '18 at 10:33
as `checkNo` seems to be full of *syncrhonous* code, you don't need a callback anyway — Jaromanda X, May 08 '18 at 10:36

score 1 · Accepted Answer · edited May 08 '18 at 12:15

While calling the function you are not using callback functionality. Change it to the normal function definition like below.

CheckNo: function () {
var comboQuery = Ext.ComponentQuery.query('[name=foocombo]')[0].getSelectedRecord();
var chkno = comboQuery.get('mychkno'); //Success to get this integer value

return chkno; //Error raises here. Debugger says "callback is not a function"
//if (callback) callback(chkno); //I've tried to check callback but did not work as well.

}

To understand how the callback works, please use below link:

This StackOverflow question

score 1 · Answer 2 · answered May 08 '18 at 10:41

1

me.checkNo(function(){ return checkNo;})

answered May 08 '18 at 10:41

John Willson

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Javascript: Why can not get variable in callback function?

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