Bootstrap loading buttons not working

I have tried this jQuery of using Bootstrap 3 buttons to use as a loading button http://www.jqueryscript.net/loading/jQuery-Plugin-For-Built-In-Loading-Indicator-In-Buttons-Button-Loader.html but on the Javascript part, it's not working for some reason when I looked into Google Chrome, it said "Uncaught TypeError: Cannot read property 'click' of null"

here's my code:

$(document).ready(function () {

    

    $('.has-spinner').click(function () {

        var btn = $(this);

        $(btn).buttonLoader('start');

        setTimeout(function () {

            $(btn).buttonLoader('stop');

        }, 3000);

    });

});

help???