JSFiddle - React, Tailwind, and code Playground

JavaScript

(function ($) {
    var c$ = {};
    
    c$.TestScope = function () {
        
        this.doAjax = function (onComplete) {
            var self = this;
            $.ajax({
                url: 'badurl',
                complete: function (data) {
                    alert('doAjax2 self === c$.oTestScope: ' + (self === c$.oTestScope).toString());
                    onComplete(data);
                }
            });
            alert('doAjax1 self === c$.oTestScope: ' + (self === c$.oTestScope).toString());  
        };
        
        this.doStuff = function (data) {
            var self = this;
            alert('doStuff self === c$.oTestScope: ' + (self === c$.oTestScope).toString());
        }
        
    };
    
    c$.oTestScope = new c$.TestScope();
    c$.oTestScope.doAjax(c$.oTestScope.doStuff);
})(jQuery);