how to correctly call a callback function for an JSON object

Question

Details:

I am getting data for the html5 Geolocation; specifically longitude and latitude. I am trying to create a plugin that anyone can call from within a project and get the long and lat.

I have read this How to return response from an ajax call but I wondering how I should call these functions.

I placed a extjs tag even though I think it's more of a javascript core question

JavaScript:

Ext.define('Ext.ux.GeoLocation', {
    alias: 'plugin.ux.geolocation',

    constructor: function() {
        console.log('called 1');
        this.duh = 'yes';
        this.init();

    },

    init: function () {
        console.log('called 2');
        navigator.geolocation.getCurrentPosition(this.test, this.test);        
    },

    test: function(init) {
        console.log('called 3');
        this.duh = "amazing";
    }

});

var geo = new Ext.ux.GeoLocation();
geo.test(); // this gets called twice though... incorrect?

Here is a FIDDLE

The console out output is:

called 1 
called 2 
called 3 
called 3

Is this a bad practice? Is there another solution?

Pablo Fernandez · Accepted Answer · 2013-12-26 16:47:15Z

2

On your class constructor you're passing the test function to navigator.geolocation.getCurrentPosition. Do you know what that other function do? most likely is calling test internally.

You can check by doing:

var geo = new Ext.ux.GeoLocation();
console.log("middle");
geo.test();

Then you should see "middle" printed between the two "called 3" lines.

answered Dec 26, 2013 at 16:47

Pablo Fernandez

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4 Comments

Phil Over a year ago

So, am I fine with just calling geo.test()? At this point by the time I get to geo.test() the getCurrentPosition() has already fired... correct?

Pablo Fernandez Over a year ago

I don't know extjs but it seems that "init" is some kind of "constructor" that gets invoked on object construction. So yes, getCurrentPosition() is getting executed on object construction (that's why you also see the "called 2" printed before "called 3")

Phil Over a year ago

I'm calling this.init() in the constructor. The constructor gets called internally. I actually removed init() and it still works...

Phil Over a year ago

nope, I was asking the wrong question. what i was looking for was impossible for javascript, your answer let me to it though, so thank you :)

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