JSFiddle - React, Tailwind, and code Playground

JavaScript

$.ajax({
            type: "POST",
            url : "http://api.yutagz.com/users",
            data: "test=test",
            success : function(data){
                alert("OK : "+data);
                console.log(data);
            },
            error:function (xhr, errorType, thrownError){
                console.log(xhr); 
                //=>no responseText but i'm sure the api send it
                //=>xhr.status = 0 ... :|
                switch (xhr.status) {
                    case 404: alert("404");
                    case 400: alert( xhr.responseText );
                         // Take action, referencing xhr.responseText as needed.
                }
            } 
          });