The problem of using axios to send request and intercept returned data by Mock in React

I use axios to send the request in js. The code is as follows:
handelOne = () = > {

    const url = "http://one.json";
    axios.get(url,{dataType:"json"})
        .then((res) => {
            let dataStr = JSON.stringify(res.data);
            console.log("1:"+dataStr);
        })
The code for the

}
mock file is:
Mock.mock ("http://one.json",{

"
//list1-5
"list|1-5":[{
    //sid11
    "sid|+1":1,
    //userId5
    "userId|5":""
}]
//"string|1-10": "" mock

})

the output of the console console is: I am requesting 1: [object,object], why is it not a specific json object but [object,object]

Mar.12,2021
Menu