JSFiddle - React, Tailwind, and code Playground

JavaScript

function custom_isset() {
        if (typeof(totally)!=='undefined'){
            if (typeof(totally['inexistent'])!=='undefined') {
                if (typeof(totally['inexistent'].property)!=='undefined') {
                    return true;
                }
            }
        }
    return false;
}
function is_it_set() {
    alert("is it set?: "+(custom_isset() ? 'Yes' : 'No'));
}
is_it_set();
var totally = {inexistent:{'property':'foo'}};
is_it_set();