$.ajax({
             type: "GET",
             url: "test.json",
             data: {username:$("#username").val(), content:$("#content").val()},
             dataType: "json",
             success: function(data){
                         console.log(data);
                      }
         });

fetch(‘/list/column‘)
            .then((response) => {
                return response.json();
            })
            .then((data) => {
                console.log(data);
                this.setState({
                    data: JSON.stringify(data)
                });
                // console.log(this.state.data);
            })
            .catch((ex) => {
                console.log(ex);
            });